UPDATE: this issue turned out to be part of a larger issue with a failing logic board on my macbook pro. RubyMine continues to be an awesome IDE for Rails development.
RubyMine is a pretty sweet IDE. I've been using it for a few versions now, including the current 2.0 beta.
However, I hit snag when I upgraded my Mac to Snow Leopard this weekend -- RubyMine was showing gibberish for any file I opened. Apparently, RubyMine is trying to use a font which doesn't exist on my upgraded Snow Leopard system. A quick fix is to go into RubyMine's preferences->fonts:
And change it to another monospaced font of your choosing. Hope this helps someone who encounters the same issue.