title: Getting rid of ActionController::InvalidAuthenticityToken (Rails 3, webrick, devise)
body: <p>Cannot figure this one out.  Developing Rails 3.0.3 app using Devise 1.1.5, running locally on WEBrick 1.3.1.  Out of nowhere I get a </p>
  
  <pre><code>ActionController::InvalidAuthenticityToken
  </code></pre>
  
  <p>error on login (successful or not) and registration.  The app is deployed to Heroku, and works fine in production.  It also works fine on another dev's machine, running on Apache/Passenger.  No matter what I do I can't get rid of this error locally (and it ran fine several days ago until this error popped up mid-development). </p>
  
  <p>I've checked out fresh code, restarted machine, run on different ports, wiped out db, everything I can think of.  No caching in the app. </p>
  
  <p>Application trace is blank. Full trace below:</p>
  
  <pre><code>actionpack (3.0.3) lib/action_controller/metal/request_forgery_protection.rb:96:in `verify_authenticity_token'
  activesupport (3.0.3) lib/active_support/callbacks.rb:441:in `_run__2106070066__process_action__1623385099__callbacks'
  activesupport (3.0.3) lib/active_support/callbacks.rb:409:in `send'
  activesupport (3.0.3) lib/active_support/callbacks.rb:409:in `_run_process_action_callbacks'
  activesupport (3.0.3) lib/active_support/callbacks.rb:93:in `send'
  activesupport (3.0.3) lib/active_support/callbacks.rb:93:in `run_callbacks'
  actionpack (3.0.3) lib/abstract_controller/callbacks.rb:17:in `process_action'
  actionpack (3.0.3) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
  activesupport (3.0.3) lib/active_support/notifications.rb:52:in `instrument'
  activesupport (3.0.3) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
  activesupport (3.0.3) lib/active_support/notifications.rb:52:in `instrument'
  actionpack (3.0.3) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
  actionpack (3.0.3) lib/action_controller/metal/rescue.rb:17:in `process_action'
  actionpack (3.0.3) lib/abstract_controller/base.rb:120:in `process'
  actionpack (3.0.3) lib/abstract_controller/rendering.rb:40:in `process'
  actionpack (3.0.3) lib/action_controller/metal.rb:138:in `dispatch'
  actionpack (3.0.3) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
  actionpack (3.0.3) lib/action_controller/metal.rb:178:in `action'
  actionpack (3.0.3) lib/action_dispatch/routing/route_set.rb:62:in `call'
  actionpack (3.0.3) lib/action_dispatch/routing/route_set.rb:62:in `dispatch'
  actionpack (3.0.3) lib/action_dispatch/routing/route_set.rb:27:in `call'
  actionpack (3.0.3) lib/action_dispatch/routing/mapper.rb:35:in `call'
  rack-mount (0.6.13) lib/rack/mount/route_set.rb:148:in `call'
  rack-mount (0.6.13) lib/rack/mount/code_generation.rb:93:in `recognize'
  rack-mount (0.6.13) lib/rack/mount/code_generation.rb:68:in `optimized_each'
  rack-mount (0.6.13) lib/rack/mount/code_generation.rb:92:in `recognize'
  rack-mount (0.6.13) lib/rack/mount/route_set.rb:139:in `call'
  actionpack (3.0.3) lib/action_dispatch/routing/route_set.rb:492:in `call'
  warden (1.0.3) lib/warden/manager.rb:35:in `call'
  warden (1.0.3) lib/warden/manager.rb:34:in `catch'
  warden (1.0.3) lib/warden/manager.rb:34:in `call'
  actionpack (3.0.3) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
  actionpack (3.0.3) lib/action_dispatch/middleware/head.rb:14:in `call'
  rack (1.2.1) lib/rack/methodoverride.rb:24:in `call'
  actionpack (3.0.3) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
  actionpack (3.0.3) lib/action_dispatch/middleware/flash.rb:182:in `call'
  actionpack (3.0.3) lib/action_dispatch/middleware/session/abstract_store.rb:149:in `call'
  actionpack (3.0.3) lib/action_dispatch/middleware/cookies.rb:295:in `call'
  activerecord (3.0.3) lib/active_record/query_cache.rb:32:in `call'
  activerecord (3.0.3) lib/active_record/connection_adapters/abstract/query_cache.rb:28:in `cache'
  activerecord (3.0.3) lib/active_record/query_cache.rb:12:in `cache'
  activerecord (3.0.3) lib/active_record/query_cache.rb:31:in `call'
  activerecord (3.0.3) lib/active_record/connection_adapters/abstract/connection_pool.rb:353:in `call'
  actionpack (3.0.3) lib/action_dispatch/middleware/callbacks.rb:46:in `call'
  activesupport (3.0.3) lib/active_support/callbacks.rb:415:in `_run_call_callbacks'
  actionpack (3.0.3) lib/action_dispatch/middleware/callbacks.rb:44:in `call'
  rack (1.2.1) lib/rack/sendfile.rb:107:in `call'
  actionpack (3.0.3) lib/action_dispatch/middleware/remote_ip.rb:48:in `call'
  actionpack (3.0.3) lib/action_dispatch/middleware/show_exceptions.rb:46:in `call'
  railties (3.0.3) lib/rails/rack/logger.rb:13:in `call'
  rack (1.2.1) lib/rack/runtime.rb:17:in `call'
  activesupport (3.0.3) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
  rack (1.2.1) lib/rack/lock.rb:11:in `call'
  rack (1.2.1) lib/rack/lock.rb:11:in `synchronize'
  rack (1.2.1) lib/rack/lock.rb:11:in `call'
  actionpack (3.0.3) lib/action_dispatch/middleware/static.rb:30:in `call'
  railties (3.0.3) lib/rails/application.rb:168:in `call'
  railties (3.0.3) lib/rails/application.rb:77:in `send'
  railties (3.0.3) lib/rails/application.rb:77:in `method_missing'
  railties (3.0.3) lib/rails/rack/log_tailer.rb:14:in `call'
  rack (1.2.1) lib/rack/content_length.rb:13:in `call'
  rack (1.2.1) lib/rack/handler/webrick.rb:52:in `service'
  /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/httpserver.rb:104:in `service'
  /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/httpserver.rb:65:in `run'
  /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:173:in `start_thread'
  /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:162:in `start'
  /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:162:in `start_thread'
  /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:95:in `start'
  /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:92:in `each'
  /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:92:in `start'
  /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:23:in `start'
  /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:82:in `start'
  rack (1.2.1) lib/rack/handler/webrick.rb:13:in `run'
  rack (1.2.1) lib/rack/server.rb:213:in `start'
  railties (3.0.3) lib/rails/commands/server.rb:65:in `start'
  railties (3.0.3) lib/rails/commands.rb:30
  railties (3.0.3) lib/rails/commands.rb:27:in `tap'
  railties (3.0.3) lib/rails/commands.rb:27
  script/rails:6:in `require'
  script/rails:6
  </code></pre>
  
  <p>Any help is appreciated!</p>
  
  <p><strong>Edit</strong>:  Here's the post from the log:</p>
  
  <pre><code>Started POST "/users/sign_in" for 127.0.0.1 at Thu Jan 13 11:04:43 -0700 2011
    Processing by Users::SessionsController#create as HTML
    Parameters: {"commit"=&gt;"Sign in", "authenticity_token"=&gt;"5R+ZYh3w/GiQwTdXExqj5O1u7Jkhrg2wclO1jfYvP5k=", "utf8"=&gt;"✓", "user"=&gt;{"remember_me"=&gt;"0", "password"=&gt;"[FILTERED]", "email"=&gt;"jason.lynes@gmail.com"}}
  Completed   in 1ms
  
  ActionController::InvalidAuthenticityToken (ActionController::InvalidAuthenticityToken):
  </code></pre>