omni補完がエラる

-- Omni completion (^O^N^P) -- Searching...Missing the Rails 2.1.0 gem. Please `gem install -v=2.1.0 rails`, update your RAILS_GEM_VERSION setting in config/environment.rb for the Rails version you do have installed, or comment out RAILS_GEM_VERSION to use the latest version installed.

エー・・
どこをさがしてるんですか・・

rails 2.1はいってますけど