Redmine

Hello Forum

I've installed redmine from Debian repository few weeks ago. Debian version is 5.0, Redmine package version is 1.0.1-1~bpo50+1.
In the meantime I created 3 projects with very low activity (some wiki-edits, few issues). Today, while adding some issues, at some point (when posting issue data) the server returned HTTP code 500. I've since restarted apache and even restarted the server, but the problem persists. Other web-resources on this server are not affected.

A look at apache error log reveals

...
[Sat Sep 24 15:42:50 2011] [error] [client 192.168.0.1] Premature end of script headers: redmine
[ pid=4742 file=ext/apache2/Hooks.cpp:713 time=2011-09-24 15:42:50.738 ]:
  The backend application (process 4869) didn't send a valid HTTP response. It might have crashed during the middle of sending an HTTP response, so please check whether there are crashing problems in your application. This is the data that it sent: [X-Powered-By]
*** Exception NoMethodError in application (undefined method `each' for nil:NilClass) (process 4869):
    from /usr/lib/ruby/1.8/phusion_passenger/rack/request_handler.rb:96:in `process_request'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_request_handler.rb:207:in `main_loop'
    from /usr/lib/ruby/1.8/phusion_passenger/railz/application_spawner.rb:418:in `start_request_handler'
    from /usr/lib/ruby/1.8/phusion_passenger/railz/application_spawner.rb:358:in `handle_spawn_application'
    from /usr/lib/ruby/1.8/phusion_passenger/utils.rb:184:in `safe_fork'
    from /usr/lib/ruby/1.8/phusion_passenger/railz/application_spawner.rb:354:in `handle_spawn_application'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `__send__'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `main_loop'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:163:in `start'
    from /usr/lib/ruby/1.8/phusion_passenger/railz/application_spawner.rb:213:in `start'
    from /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:262:in `spawn_rails_application'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server_collection.rb:126:in `lookup_or_add'
    from /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:256:in `spawn_rails_application'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server_collection.rb:80:in `synchronize'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server_collection.rb:79:in `synchronize'
    from /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:255:in `spawn_rails_application'
    from /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:154:in `spawn_application'
    from /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:287:in `handle_spawn_application'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `__send__'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `main_loop'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
    from /usr/lib/phusion_passenger/passenger-spawn-server:61
Error during failsafe response: Shifting failed. closed stream
[Sat Sep 24 15:42:51 2011] [error] [client 192.168.0.1] Premature end of script headers: redmine
[ pid=4743 file=ext/apache2/Hooks.cpp:713 time=2011-09-24 15:42:51.20 ]:
  The backend application (process 4872) didn't send a valid HTTP response. It might have crashed during the middle of sending an HTTP response, so please check whether there are crashing problems in your application. This is the data that it sent: [X-Powered-By]
*** Exception NoMethodError in application (undefined method `each' for nil:NilClass) (process 4872):
    from /usr/lib/ruby/1.8/phusion_passenger/rack/request_handler.rb:96:in `process_request'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_request_handler.rb:207:in `main_loop'
    from /usr/lib/ruby/1.8/phusion_passenger/railz/application_spawner.rb:418:in `start_request_handler'
    from /usr/lib/ruby/1.8/phusion_passenger/railz/application_spawner.rb:358:in `handle_spawn_application'
    from /usr/lib/ruby/1.8/phusion_passenger/utils.rb:184:in `safe_fork'
    from /usr/lib/ruby/1.8/phusion_passenger/railz/application_spawner.rb:354:in `handle_spawn_application'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `__send__'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `main_loop'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:163:in `start'
    from /usr/lib/ruby/1.8/phusion_passenger/railz/application_spawner.rb:213:in `start'
    from /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:262:in `spawn_rails_application'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server_collection.rb:126:in `lookup_or_add'
    from /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:256:in `spawn_rails_application'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server_collection.rb:80:in `synchronize'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server_collection.rb:79:in `synchronize'
    from /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:255:in `spawn_rails_application'
    from /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:154:in `spawn_application'
    from /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:287:in `handle_spawn_application'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `__send__'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `main_loop'
    from /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
    from /usr/lib/phusion_passenger/passenger-spawn-server:61
...

I'm a developer, but with zero ruby / rails knowledge, so it's hard for me to further investigate on this.
Anyone knows what may be going on here?