Ruby 1.9.1-p234, Passenger 2.2.5, Rails 2.3-stable closed stream on POST request

Question

I've setup Ruby 1.9.1 (p234) on a Ubuntu server. I'm trying to deploy a Rails app which vendors Rails 2.3-stable on Apache 2.2/Passenger 2.2.5.

GET requests work fine, POST requests break immediately with the following log entry:

Processing UsersController#new (for 80.203.77.44 at 2009-10-24 20:54:55) [GET]
  Parameters: {"controller"=>"users", "action"=>"new"}
Rendering template within layouts/application
Rendering users/new
Completed in 23ms (View: 20, DB: 0) | 200 OK [http://myapp/user/new]
/!\ FAILSAFE /!\  2009-10-24 20:55:01 +0200
  Status: 500 Internal Server Error
  closed stream
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/vendor/rack-1.0.0-git/lib/rack/rewindable_input.rb:86:in make_rewindable'
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/vendor/rack-1.0.0-git/lib/rack/rewindable_input.rb:26:inread'
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/vendor/rack-1.0.0-git/lib/rack/request.rb:136:in POST'
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/vendor/rack-1.0.0-git/lib/rack/methodoverride.rb:15:incall'
    /var/www/myapp/app/releases/20091021213913/vendor/rails/actionpack/lib/action_controller/params_parser.rb:15:in call'
    /var/www/myapp/app/releases/20091021213913/vendor/rails/actionpack/lib/action_controller/session/cookie_store.rb:93:incall'
    /var/www/myapp/app/releases/20091021213913/vendor/rails/actionpack/lib/action_controller/failsafe.rb:26:in call'
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/vendor/rack-1.0.0-git/lib/rack/lock.rb:11:inblock in call'
    :8:in synchronize'
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/vendor/rack-1.0.0-git/lib/rack/lock.rb:11:incall'
    /var/www/myapp/app/releases/20091021213913/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:106:in call'
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/lib/phusion_passenger/rack/request_handler.rb:95:inprocess_request'
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/lib/phusion_passenger/abstract_request_handler.rb:207:in main_loop'
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/lib/phusion_passenger/railz/application_spawner.rb:378:instart_request_handler'
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/lib/phusion_passenger/railz/application_spawner.rb:336:in block in handle_spawn_application'
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/lib/phusion_passenger/utils.rb:183:insafe_fork'
    /usr/local/lib/ruby/gems/1.9.1/gems/passenger-2.2.5/lib/phusion_passenger/railz/application_spawner.rb:334:in `handle_spawn_application'

...and then some.

I've read up, and found this: http://blog.labnotes.org/2009/09/01/ruby-1-9-1-p234passenger-2-2-5-tempfile-rb-fix/ which points to a patch that removes a single line from Ruby 1.9.1-p234's tempfile.rb. Unfortunately for me, inspecting that file I find that the offensive line has already been removed. So that leaves me a bit clueless, as my problem persists. Any ideas?