File size upload issue

We use WAGN v1.5.3 and nginx (client_max_body_size 500M). Uploading a 100MB file is fine, uploading a 200MB breaks with the following:

Processing CardFilesController#create (for 192.168.50.10 at 2011-05-10 11:28:57) [POST]

  Parameters: {"card_file"=>{"uploaded_data"=>#<File:/tmp/RackMultipart16639-0>, "attachment_uuid"=>"748316037914393851037778106034", "type"=>"CardFile"}}

ActionView::MissingTemplate (Missing template card_files/new.erb in view path app/views:vendor/plugins/exception_notification/lib/../views):

  /usr/lib/ruby/gems/1.8/gems/hoptoad_notifier-2.4.9/lib/hoptoad_notifier/rack.rb:27:in `call'

  /usr/lib/ruby/gems/1.8/gems/hoptoad_notifier-2.4.9/lib/hoptoad_notifier/user_informer.rb:12:in `call'

  passenger (2.2.15) lib/phusion_passenger/rack/request_handler.rb:92:in `process_request'

  passenger (2.2.15) lib/phusion_passenger/abstract_request_handler.rb:207:in `main_loop'

  passenger (2.2.15) lib/phusion_passenger/railz/application_spawner.rb:441:in `start_request_handler'

  passenger (2.2.15) lib/phusion_passenger/railz/application_spawner.rb:381:in `handle_spawn_application'

  passenger (2.2.15) lib/phusion_passenger/utils.rb:252:in `safe_fork'

  passenger (2.2.15) lib/phusion_passenger/railz/application_spawner.rb:377:in `handle_spawn_application'

  passenger (2.2.15) lib/phusion_passenger/abstract_server.rb:352:in `__send__'

  passenger (2.2.15) lib/phusion_passenger/abstract_server.rb:352:in `main_loop'

  passenger (2.2.15) lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously'

  passenger (2.2.15) lib/phusion_passenger/abstract_server.rb:163:in `start'

  passenger (2.2.15) lib/phusion_passenger/railz/application_spawner.rb:222:in `start'

  passenger (2.2.15) lib/phusion_passenger/spawn_manager.rb:253:in `spawn_rails_application'

  passenger (2.2.15) lib/phusion_passenger/abstract_server_collection.rb:126:in `lookup_or_add'

  passenger (2.2.15) lib/phusion_passenger/spawn_manager.rb:247:in `spawn_rails_application'

  passenger (2.2.15) lib/phusion_passenger/abstract_server_collection.rb:80:in `synchronize'

  passenger (2.2.15) lib/phusion_passenger/abstract_server_collection.rb:79:in `synchronize'

  passenger (2.2.15) lib/phusion_passenger/spawn_manager.rb:246:in `spawn_rails_application'

  passenger (2.2.15) lib/phusion_passenger/spawn_manager.rb:145:in `spawn_application'

  passenger (2.2.15) lib/phusion_passenger/spawn_manager.rb:278:in `handle_spawn_application'

  passenger (2.2.15) lib/phusion_passenger/abstract_server.rb:352:in `__send__'

  passenger (2.2.15) lib/phusion_passenger/abstract_server.rb:352:in `main_loop'

  passenger (2.2.15) lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously'

** [Hoptoad] Timeout while contacting the Hoptoad server.

** [Hoptoad] Environment Info: [Ruby: 1.8.7] [Rails: 2.3.5] [Env: production]

** [Hoptoad] Failure: NilClass

** [Hoptoad] Environment Info: [Ruby: 1.8.7] [Rails: 2.3.5] [Env: production]

Rendering /var/www/wagn-rms/public/500.html (500 Internal Server Error)

Any advice where I can start trying to find this issue?