Defect is detected with redmine r5506 and a workaround is to comment line 120, in app/controllers/projects_controller.rb:

        @project.enabled_module_names = params[:enabled_modules]

I think that, anyway, this line is not good because here is an extract of the log file and controller should use params[:project][:enabled_module_names]:

bq. Processing ProjectsController#copy (for 132.166.52.226 at 2011-04-28 16:40:17) [POST]
Parameters: {"only"=>["members", "versions", "issue_categories", "issues", "queries", "boards", "wiki", ""], "commit"=>"Copier", "project"=>{"issue_custom_field_ids"=>[""], "name"=>"pipo", "enabled_module_names"=>["issue_tracking", "wiki", "repository", "calendar", "gantt", "bigbluebutton", "doodles", "scm_extensions", "synapse", "webdav", "wiki_extensions", ""], "tracker_ids"=>["3", "6", ""], "description"=>"", "homepage"=>"", "is_public"=>"0", "identifier"=>"pipo", "parent_id"=>"", "custom_field_values"=>{"7"=>""}}, "action"=>"copy", "authenticity_token"=>"XXXXXXXXXX", "id"=>"template-synapse", "controller"=>"projects"}

Kind regards,
Arnaud