Error while initializng temporary session directories in edg

I’m encountering an odd error when starting up apps running Edge on my
production server (or in the console). The same app works fine in
deployment mode on a different machine. Note, this seems to be only a
problem with edge, as i run several apps under 1.2.1 on the same
server and do not have any problems. Here is the full stack-trace:

./script/…/config/…/vendor/rails/activesupport/lib/active_support/
dependencies.rb:263:in load_missing_constant': uninitialized constant ActionController::CgiRequest (NameError) from ./script/../config/../vendor/rails/activesupport/lib/ active_support/dependencies.rb:452:inconst_missing’
from /usr/lib/ruby/gems/1.8/gems/actionpack-1.13.1/lib/
action_controller/session_management.rb:34:in session_options' from ./script/../config/../vendor/rails/railties/lib/ initializer.rb:311:ininitialize_temporary_directories’
from ./script/…/config/…/vendor/rails/railties/lib/
initializer.rb:100:in process' from ./script/../config/../vendor/rails/railties/lib/ initializer.rb:46:inrun’
from /home/railsapps/fivechimes/releases/20070307070003/config/
environment.rb:13
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:
27:in require' from ./script/../config/../vendor/rails/activesupport/lib/ active_support/dependencies.rb:495:inrequire’
… 16 levels…
from ./script/…/config/…/vendor/rails/activesupport/lib/
active_support/dependencies.rb:342:in new_constants_in' from ./script/../config/../vendor/rails/activesupport/lib/ active_support/dependencies.rb:495:inrequire’
from ./script/…/config/…/vendor/rails/railties/lib/commands/
server.rb:39
from script/server:3

What i find strange is that at one point it seems to look for
session_management.rb in the gem (?), while the vendor directory is
clearly present and is otherwise used. It also seems to be related to
Session management, which was recently changed (i use
ActiveRecordStore and not the new default). FYI, line 13 in
environment.rb is where the Rails::Initializer block starts. Does
anybody have any ideas?