Phusion Passenger/ruby 1.9.3/rails 3.1.3 / [ASYNC BUG] thread_timer: select-Collection of common programming errors

I just upgraded to Ruby 1.9.3-p0 and Rails 3.1.3. And then I re-installed Phusion Passenger with support for nginx. Now nginx is recording the following error on every page access:

[ASYNC BUG] thread_timer: select EBADF

ruby 1.9.3p0 (2011-10-30) [x86_64-linux]

[NOTE] You may have encountered a bug in the Ruby interpreter or extension libraries. Bug reports are welcome. For details: http://www.ruby-lang.org/bugreport.html

All of this is on Ubuntu 11.4.

The error trace in the browser looks like this:

Passenger encountered the following error:

The application spawner server exited unexpectedly: Unexpected end-of-file detected.

Exception class:
    PhusionPassenger::Rack::ApplicationSpawner::Error

#   File                                                                                    Line    Location
0   /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/rack/application_spawner.rb    134     in `rescue in start'
1   /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/rack/application_spawner.rb    129     in `start'
2   /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/spawn_manager.rb   253     in `block (2 levels) in spawn_rack_application'
3   /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server_collection.rb  132     in `lookup_or_add'
4   /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/spawn_manager.rb   246     in `block in spawn_rack_application'
5   /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server_collection.rb  82  in `block in synchronize'
6   < td="">  prelude>    10:in `synchronize'
7   /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server_collection.rb  79  in `synchronize'
8   /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/spawn_manager.rb   244     in `spawn_rack_application'
9   /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/spawn_manager.rb   137     in `spawn_application'
10  /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/spawn_manager.rb   275     in `handle_spawn_application'
11  /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server.rb     357     in `server_main_loop'
12  /opt/gem_home/gems/passenger-3.0.9/lib/phusion_passenger/abstract_server.rb     206     in `start_synchronously'
13  /opt/gem_home/gems/passenger-3.0.9/helper-scripts/passenger-spawn-server

Any ideas on how to fix this?