Updated Sep 14th, 2012
Dreamhost + Rails = Explode
You have already activated rack 1.2.1, but your Gemfile requires rack 1.2.3.
gem 'rack', '1.2.1' # add this to Gemfile
The problem with this error, is that even though you've fixed the Gemfile, you've accidentally installed rack-1.2.3 by triggering this error! So we need to track down that update and delete it.
- goto ~/.gems/gems/ on your server
- delete rack-1.2.3
The application has exited during startup (i.e. during the evaluation of config/environment.rb).
- delete Gemfile.lock
- rebuild it (use bundle install)