We have the same issue. Ruby 1.8.7 seems to be the trigger. Looks like something is missing/broken in Ruby.

This seems to be backed up by this post:
http://yehudakatz.com/2010/01/02/the-craziest-fing-bug-ive-ever-seen/

Our log File:

Started GET "/projects/adpress/issues.pdf" for 76.26.193.219 at Thu May 24 20:57:11 -0400 2012

NoMethodError (undefined method `to_ary' for #<Mime::Type:0xb76b58ac>):
actionpack (3.2.3) lib/action_dispatch/http/mime_type.rb:270:in `method_missing'
actionpack (3.2.3) lib/action_dispatch/http/mime_negotiation.rb:55:in `Array'
actionpack (3.2.3) lib/action_dispatch/http/mime_negotiation.rb:55:in `formats'
actionpack (3.2.3) lib/action_dispatch/http/mime_negotiation.rb:49:in `format'
actionpack (3.2.3) lib/action_controller/metal/instrumentation.rb:22:in `process_action'
actionpack (3.2.3) lib/action_controller/metal/params_wrapper.rb:205:in `process_action'
activerecord (3.2.3) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.2.3) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.2.3) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.2.3) lib/action_controller/metal.rb:203:in `dispatch'
actionpack (3.2.3) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.2.3) lib/action_controller/metal.rb:246:in `action'
actionpack (3.2.3) lib/action_dispatch/routing/route_set.rb:73:in `call'
actionpack (3.2.3) lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
actionpack (3.2.3) lib/action_dispatch/routing/route_set.rb:36:in `call'
journey (1.0.3) lib/journey/router.rb:68:in `call'
journey (1.0.3) lib/journey/router.rb:56:in `each'
journey (1.0.3) lib/journey/router.rb:56:in `call'
actionpack (3.2.3) lib/action_dispatch/routing/route_set.rb:600:in `call'
rack-openid (1.3.1) lib/rack/openid.rb:98:in `call'
actionpack (3.2.3) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.4.1) lib/rack/etag.rb:23:in `call'
rack (1.4.1) lib/rack/conditionalget.rb:25:in `call'
actionpack (3.2.3) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.2.3) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.2.3) lib/action_dispatch/middleware/flash.rb:242:in `call'
rack (1.4.1) lib/rack/session/abstract/id.rb:205:in `context'
rack (1.4.1) lib/rack/session/abstract/id.rb:200:in `call'
actionpack (3.2.3) lib/action_dispatch/middleware/cookies.rb:338:in `call'
activerecord (3.2.3) lib/active_record/query_cache.rb:64:in `call'
activerecord (3.2.3) lib/active_record/connection_adapters/abstract/connection_pool.rb:467:in `call'
actionpack (3.2.3) lib/action_dispatch/middleware/callbacks.rb:28:in `call'
activesupport (3.2.3) lib/active_support/callbacks.rb:405:in `_run__397314981__call__4__callbacks'
activesupport (3.2.3) lib/active_support/callbacks.rb:405:in `send'
activesupport (3.2.3) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.3) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
activesupport (3.2.3) lib/active_support/callbacks.rb:81:in `send'
activesupport (3.2.3) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.3) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (3.2.3) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
actionpack (3.2.3) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
actionpack (3.2.3) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
railties (3.2.3) lib/rails/rack/logger.rb:26:in `call_app'
railties (3.2.3) lib/rails/rack/logger.rb:16:in `call'
actionpack (3.2.3) lib/action_dispatch/middleware/request_id.rb:22:in `call'
rack (1.4.1) lib/rack/methodoverride.rb:21:in `call'
rack (1.4.1) lib/rack/runtime.rb:17:in `call'
activesupport (3.2.3) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.4.1) lib/rack/lock.rb:15:in `call'
actionpack (3.2.3) lib/action_dispatch/middleware/static.rb:62:in `call'
rack-cache (1.2) lib/rack/cache/context.rb:136:in `forward'
rack-cache (1.2) lib/rack/cache/context.rb:245:in `fetch'
rack-cache (1.2) lib/rack/cache/context.rb:185:in `lookup'
rack-cache (1.2) lib/rack/cache/context.rb:66:in `call!'
rack-cache (1.2) lib/rack/cache/context.rb:51:in `call'
railties (3.2.3) lib/rails/engine.rb:479:in `call'
railties (3.2.3) lib/rails/application.rb:220:in `call'
railties (3.2.3) lib/rails/railtie/configurable.rb:30:in `send'
railties (3.2.3) lib/rails/railtie/configurable.rb:30:in `method_missing'
passenger (2.2.11) lib/phusion_passenger/rack/request_handler.rb:92:in `process_request'
passenger (2.2.11) lib/phusion_passenger/abstract_request_handler.rb:207:in `main_loop'
passenger (2.2.11) lib/phusion_passenger/rack/application_spawner.rb:118:in `run'
passenger (2.2.11) lib/phusion_passenger/rack/application_spawner.rb:65:in `spawn_application'
passenger (2.2.11) lib/phusion_passenger/utils.rb:184:in `safe_fork'
passenger (2.2.11) lib/phusion_passenger/rack/application_spawner.rb:58:in `spawn_application'
passenger (2.2.11) lib/phusion_passenger/rack/application_spawner.rb:41:in `spawn_application'
passenger (2.2.11) lib/phusion_passenger/spawn_manager.rb:159:in `spawn_application'
passenger (2.2.11) lib/phusion_passenger/spawn_manager.rb:287:in `handle_spawn_application'
passenger (2.2.11) lib/phusion_passenger/abstract_server.rb:352:in `__send__'
passenger (2.2.11) lib/phusion_passenger/abstract_server.rb:352:in `main_loop'
passenger (2.2.11) lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
passenger (2.2.11) bin/passenger-spawn-server:61

--------------------------------------------------------------------------------
I can't reproduce with 1.4.1 and ruby1.8.7.
--------------------------------------------------------------------------------
I have the same problem.
--------------------------------------------------------------------------------
Is there possibly a gem or something with Passenger that triggers the problem?

Apache + Passenger + Ruby + Rails with Redmine 2.0 cannot export CSV, PDF, or the RSS Atom. They all product an error similar to the one output by the Passenger logging in Ruby as noted above.

What can we do to help isolate and track down the issue?
--------------------------------------------------------------------------------
Same problem for me : no export possible in txt, html or pdf
just upgrade to redmine 2.0.3

Started GET "/projets/projects/gfcpv2/wiki/Requirements.txt" for XXXXXX at Wed Jun 20 21:57:33 +0200 2012

NoMethodError (undefined method `to_ary' for #<Mime::Type:0x2b9174ea4350>):
actionpack (3.2.6) lib/action_dispatch/http/mime_type.rb:270:in `method_missing'
actionpack (3.2.6) lib/action_dispatch/http/mime_negotiation.rb:55:in `Array'
actionpack (3.2.6) lib/action_dispatch/http/mime_negotiation.rb:55:in `formats'
actionpack (3.2.6) lib/action_dispatch/http/mime_negotiation.rb:49:in `format'
actionpack (3.2.6) lib/action_controller/metal/instrumentation.rb:22:in `process_action'
actionpack (3.2.6) lib/action_controller/metal/params_wrapper.rb:206:in `process_action'
activerecord (3.2.6) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.2.6) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.2.6) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.2.6) lib/action_controller/metal.rb:203:in `dispatch'
actionpack (3.2.6) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.2.6) lib/action_controller/metal.rb:246:in `action'
actionpack (3.2.6) lib/action_dispatch/routing/route_set.rb:73:in `call'
actionpack (3.2.6) lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
actionpack (3.2.6) lib/action_dispatch/routing/route_set.rb:36:in `call'
journey (1.0.4) lib/journey/router.rb:68:in `call'
journey (1.0.4) lib/journey/router.rb:56:in `each'
journey (1.0.4) lib/journey/router.rb:56:in `call'
actionpack (3.2.6) lib/action_dispatch/routing/route_set.rb:600:in `call'
rack-openid (1.3.1) lib/rack/openid.rb:98:in `call'
actionpack (3.2.6) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.4.1) lib/rack/etag.rb:23:in `call'
rack (1.4.1) lib/rack/conditionalget.rb:25:in `call'
actionpack (3.2.6) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.2.6) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.2.6) lib/action_dispatch/middleware/flash.rb:242:in `call'
rack (1.4.1) lib/rack/session/abstract/id.rb:205:in `context'
rack (1.4.1) lib/rack/session/abstract/id.rb:200:in `call'
actionpack (3.2.6) lib/action_dispatch/middleware/cookies.rb:338:in `call'
activerecord (3.2.6) lib/active_record/query_cache.rb:64:in `call'
activerecord (3.2.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:473:in `call'
actionpack (3.2.6) lib/action_dispatch/middleware/callbacks.rb:28:in `call'
activesupport (3.2.6) lib/active_support/callbacks.rb:405:in `_run__397314981__call__4__callbacks'
activesupport (3.2.6) lib/active_support/callbacks.rb:405:in `send'
activesupport (3.2.6) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.6) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
activesupport (3.2.6) lib/active_support/callbacks.rb:81:in `send'
activesupport (3.2.6) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.6) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (3.2.6) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
actionpack (3.2.6) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
actionpack (3.2.6) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
railties (3.2.6) lib/rails/rack/logger.rb:26:in `call_app'
railties (3.2.6) lib/rails/rack/logger.rb:16:in `call'
actionpack (3.2.6) lib/action_dispatch/middleware/request_id.rb:22:in `call'
rack (1.4.1) lib/rack/methodoverride.rb:21:in `call'
rack (1.4.1) lib/rack/runtime.rb:17:in `call'
activesupport (3.2.6) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.4.1) lib/rack/lock.rb:15:in `call'
actionpack (3.2.6) lib/action_dispatch/middleware/static.rb:62:in `call'
rack-cache (1.2) lib/rack/cache/context.rb:136:in `forward'
rack-cache (1.2) lib/rack/cache/context.rb:245:in `fetch'
rack-cache (1.2) lib/rack/cache/context.rb:185:in `lookup'
rack-cache (1.2) lib/rack/cache/context.rb:66:in `call!'
rack-cache (1.2) lib/rack/cache/context.rb:51:in `call'
railties (3.2.6) lib/rails/engine.rb:479:in `call'
railties (3.2.6) lib/rails/application.rb:220:in `call'
railties (3.2.6) lib/rails/railtie/configurable.rb:30:in `send'
railties (3.2.6) lib/rails/railtie/configurable.rb:30:in `method_missing'
passenger (3.0.13) lib/phusion_passenger/rack/request_handler.rb:96:in `process_request'
passenger (3.0.13) lib/phusion_passenger/abstract_request_handler.rb:516:in `accept_and_process_next_request'
passenger (3.0.13) lib/phusion_passenger/abstract_request_handler.rb:274:in `main_loop'
passenger (3.0.13) lib/phusion_passenger/classic_rails/application_spawner.rb:321:in `start_request_handler'
passenger (3.0.13) lib/phusion_passenger/classic_rails/application_spawner.rb:275:in `send'
passenger (3.0.13) lib/phusion_passenger/classic_rails/application_spawner.rb:275:in `handle_spawn_application'
passenger (3.0.13) lib/phusion_passenger/utils.rb:479:in `safe_fork'
passenger (3.0.13) lib/phusion_passenger/classic_rails/application_spawner.rb:270:in `handle_spawn_application'
passenger (3.0.13) lib/phusion_passenger/abstract_server.rb:357:in `__send__'
passenger (3.0.13) lib/phusion_passenger/abstract_server.rb:357:in `server_main_loop'
passenger (3.0.13) lib/phusion_passenger/abstract_server.rb:206:in `start_synchronously'
passenger (3.0.13) lib/phusion_passenger/abstract_server.rb:180:in `start'
passenger (3.0.13) lib/phusion_passenger/classic_rails/application_spawner.rb:149:in `start'
passenger (3.0.13) lib/phusion_passenger/spawn_manager.rb:219:in `spawn_rails_application'
passenger (3.0.13) lib/phusion_passenger/abstract_server_collection.rb:132:in `lookup_or_add'
passenger (3.0.13) lib/phusion_passenger/spawn_manager.rb:214:in `spawn_rails_application'
passenger (3.0.13) lib/phusion_passenger/abstract_server_collection.rb:82:in `synchronize'
passenger (3.0.13) lib/phusion_passenger/abstract_server_collection.rb:79:in `synchronize'
passenger (3.0.13) lib/phusion_passenger/spawn_manager.rb:213:in `spawn_rails_application'
passenger (3.0.13) lib/phusion_passenger/spawn_manager.rb:132:in `spawn_application'
passenger (3.0.13) lib/phusion_passenger/spawn_manager.rb:275:in `handle_spawn_application'
passenger (3.0.13) lib/phusion_passenger/abstract_server.rb:357:in `__send__'
passenger (3.0.13) lib/phusion_passenger/abstract_server.rb:357:in `server_main_loop'
passenger (3.0.13) lib/phusion_passenger/abstract_server.rb:206:in `start_synchronously'
passenger (3.0.13) helper-scripts/passenger-spawn-server:99

Cheers

Karim

--------------------------------------------------------------------------------
I'm having the same problem:
Redmine 2.0.3
Passenger 3.0.15
Rack 1.4.1
Ruby 1.8.7
S.O CentOS 5.8

Not work export pdf and png, not work rest webservice which displays the same error.
--------------------------------------------------------------------------------
I have find the problem:
<pre>
Array(Mime[parameters[:format]])
</pre>
the Array() method is not working, which require method: to_ary

solution:
1. actionpack (3.2.6) lib/action_dispatch/http/mime_negotiation.rb:55
change from *Array(Mime[parameters[:format]])*
to *Array.wrap(Mime[parameters[:format]])*

2. upgrade ruby to latest
I use this version, and it works.
<pre>
ruby 1.8.7 (2011-05-23 patchlevel 346) [i686-linux]
</pre>

3. maybe the latest actionpack fixed that problem?

ref:
https://rails.lighthouseapp.com/projects/8994/tickets/5599-use-arraywrap-instead-of-array
--------------------------------------------------------------------------------
I've also had this affecting me in 2.1.2.stable.10698, I'm sorry if the below problem isn't the same issue, but as far as I can tell, it is.

Info:
<pre>
Redmine version 2.1.2.stable.10698
Ruby version 1.8.7 (x86_64-linux)
Rails version 3.2.8
Environment production
Database adapter MySQL
</pre>

As stated above, this was affecting ATOM, and this is where I was getting the errors, it may be my set up however:
<pre>
Started GET "/projects/1/activity.atom?key=28cf9056229771372bdcde963a41900ffe5ad085&user_id=1" for 213.106.101.114 at Wed Oct 24 17:00:18 +0100 2012

NoMethodError (undefined method `to_ary' for #<Mime::Type:0x7fa75b70e478>):
actionpack (3.2.8) lib/action_dispatch/http/mime_type.rb:270:in `method_missing'
actionpack (3.2.8) lib/action_dispatch/http/mime_negotiation.rb:55:in `Array'
actionpack (3.2.8) lib/action_dispatch/http/mime_negotiation.rb:55:in `formats'
actionpack (3.2.8) lib/action_dispatch/http/mime_negotiation.rb:49:in `format'
actionpack (3.2.8) lib/action_controller/metal/instrumentation.rb:22:in `process_action'
actionpack (3.2.8) lib/action_controller/metal/params_wrapper.rb:207:in `process_action'
activerecord (3.2.8) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.2.8) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.2.8) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.2.8) lib/action_controller/metal.rb:203:in `dispatch'
actionpack (3.2.8) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.2.8) lib/action_controller/metal.rb:246:in `action'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:73:in `call'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:36:in `call'
journey (1.0.4) lib/journey/router.rb:68:in `call'
journey (1.0.4) lib/journey/router.rb:56:in `each'
journey (1.0.4) lib/journey/router.rb:56:in `call'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:600:in `call'
rack-openid (1.3.1) lib/rack/openid.rb:98:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.4.1) lib/rack/etag.rb:23:in `call'
rack (1.4.1) lib/rack/conditionalget.rb:25:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/flash.rb:242:in `call'
rack (1.4.1) lib/rack/session/abstract/id.rb:205:in `context'
rack (1.4.1) lib/rack/session/abstract/id.rb:200:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/cookies.rb:339:in `call'
activerecord (3.2.8) lib/active_record/query_cache.rb:64:in `call'
activerecord (3.2.8) lib/active_record/connection_adapters/abstract/connection_pool.rb:473:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/callbacks.rb:28:in `call'
activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `_run__397314981__call__4__callbacks'
activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `send'
activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.8) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
activesupport (3.2.8) lib/active_support/callbacks.rb:81:in `send'
activesupport (3.2.8) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.8) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
railties (3.2.8) lib/rails/rack/logger.rb:26:in `call_app'
railties (3.2.8) lib/rails/rack/logger.rb:16:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/request_id.rb:22:in `call'
rack (1.4.1) lib/rack/methodoverride.rb:21:in `call'
rack (1.4.1) lib/rack/runtime.rb:17:in `call'
activesupport (3.2.8) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.4.1) lib/rack/lock.rb:15:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/static.rb:62:in `call'
rack-cache (1.2) lib/rack/cache/context.rb:136:in `forward'
rack-cache (1.2) lib/rack/cache/context.rb:245:in `fetch'
rack-cache (1.2) lib/rack/cache/context.rb:185:in `lookup'
rack-cache (1.2) lib/rack/cache/context.rb:66:in `call!'
rack-cache (1.2) lib/rack/cache/context.rb:51:in `call'
railties (3.2.8) lib/rails/engine.rb:479:in `call'
railties (3.2.8) lib/rails/application.rb:223:in `call'
railties (3.2.8) lib/rails/railtie/configurable.rb:30:in `send'
railties (3.2.8) lib/rails/railtie/configurable.rb:30:in `method_missing'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/rack/request_handler.rb:96:in `process_request'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_request_handler.rb:513:in `accept_and_process_next_request'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_request_handler.rb:274:in `main_loop'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/rack/application_spawner.rb:205:in `start_request_handler'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/rack/application_spawner.rb:170:in `send'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/rack/application_spawner.rb:170:in `handle_spawn_application'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/utils.rb:479:in `safe_fork'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/rack/application_spawner.rb:165:in `handle_spawn_application'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server.rb:357:in `__send__'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server.rb:357:in `server_main_loop'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server.rb:206:in `start_synchronously'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server.rb:180:in `start'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/rack/application_spawner.rb:128:in `start'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/spawn_manager.rb:253:in `spawn_rack_application'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server_collection.rb:132:in `lookup_or_add'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/spawn_manager.rb:246:in `spawn_rack_application'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server_collection.rb:82:in `synchronize'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server_collection.rb:79:in `synchronize'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/spawn_manager.rb:244:in `spawn_rack_application'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/spawn_manager.rb:137:in `spawn_application'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/spawn_manager.rb:275:in `handle_spawn_application'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server.rb:357:in `__send__'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server.rb:357:in `server_main_loop'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server.rb:206:in `start_synchronously'
/usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.9//helper-scripts/passenger-spawn-server:99
</pre>

I have attempted solution 1, however this didn't work.
--------------------------------------------------------------------------------
Hi,
i had the same isse, see http://www.redmine.org/boards/2/topics/33950
But Solution 1 works for me

Environment:
Redmine version 2.1.0.stable
Ruby version 1.8.7 (x86_64-linux)
Rails version 3.2.8
Environment production
Database adapter MySQL

Apache+fcgid
ruby 1.8.7 (2008-05-31 patchlevel 0) [x86_64-linux]

RedhatEnterpriseServer5
--------------------------------------------------------------------------------
Reported duplicate similar problem in #12863.
I can confirm that patching the lib/action_dispatch/http/mime_negotiation.rb:55 as mentioned above has helped.
(My Action Pack is v3.2.11 bude the code at the line 55 was same as in v3.2.6)
--------------------------------------------------------------------------------
same issue:
http://www.redmine.org/issues/12076#note-8
would you please make any suggestion?
--------------------------------------------------------------------------------
<pre>
location ~ .(html|css|js) {
root /var/www/rm2.2.2/public;
expires 30d;
access_log off;
error_log off; }
</pre>
after removing "js" from nginx config file, Edit works
--------------------------------------------------------------------------------

duplicates,Closed,12076,Can't edit update of an issue
duplicates,Closed,12863,Editing messages in Issue history does not work
duplicates,Closed,13184,500 internal server error when changing tracker