heroku won't create session

Processing SessionsController#create (for 69.181.229.66 at 2010-08-26 09:51:34) [POST]
  Parameters: {"commit"=>"Sign in", "session"=>{"remember_me"=>"0", "password"=>"[FILTERED]", "login"=>"captproton"}, "action"=>"create", "authenticity_token"=>"V+3vwI8cM01NgQbWgpCvEmzgiOg59yNNQBDObD5eA1s=", "controller"=>"sessions"}

ActionController::InvalidAuthenticityToken (ActionController::InvalidAuthenticityToken):
  /home/heroku_rack/lib/static_assets.rb:9:in `call'
  /home/heroku_rack/lib/last_access.rb:25:in `call'
  /home/heroku_rack/lib/date_header.rb:14:in `call'
  thin (1.2.6) lib/thin/connection.rb:76:in `pre_process'
  thin (1.2.6) lib/thin/connection.rb:74:in `catch'
  thin (1.2.6) lib/thin/connection.rb:74:in `pre_process'
  thin (1.2.6) lib/thin/connection.rb:57:in `process'
  thin (1.2.6) lib/thin/connection.rb:42:in `receive_data'
  eventmachine (0.12.10) lib/eventmachine.rb:256:in `run_machine'
  eventmachine (0.12.10) lib/eventmachine.rb:256:in `run'
  thin (1.2.6) lib/thin/backends/base.rb:57:in `start'
  thin (1.2.6) lib/thin/server.rb:156:in `start'
  thin (1.2.6) lib/thin/controllers/controller.rb:80:in `start'
  thin (1.2.6) lib/thin/runner.rb:177:in `send'
  thin (1.2.6) lib/thin/runner.rb:177:in `run_command'
  thin (1.2.6) lib/thin/runner.rb:143:in `run!'
  thin (1.2.6) bin/thin:6
  /usr/ruby1.8.7/bin/thin:19:in `load'
  /usr/ruby1.8.7/bin/thin:19

Rendering /disk1/home/slugs/215288_a70337e_cebb/mnt/public/422.html (422 Unprocessable Entity)

==> dyno-1567341.log <==
/home/slugs/215288_a70337e_cebb/mnt/.bundle/gems/ruby/1.8/gems/authlogic-2.1.6/lib/authlogic.rb:3: warning: already initialized constant AUTHLOGIC_PATH
>> Thin web server (v1.2.6 codename Crazy Delicious)
>> Maximum connections set to 1024
>> Listening on 0.0.0.0:37930, CTRL+C to stop