mocha gem error on dreamhost

I've just signed up to dreamhost and I'm trying to set up a rails application but I get a 'Rails application failed to start properly' on the welcome screen of the rails page. I followed the instructions on the wiki page on how to set up your rails app on dreamhost. when I enter: ./dispatch.fcgi I receive the error: 'could not find Rubygem Mocha'

Anyone knows what this is about ? Thanks alot.