I've got both a personal MacBook, and a work MacBook pro, each with licensed copies of TextMate.
A few weeks back on my personal machine, I followed the instructions here to get Textmate to detect files ending in _spec.rb as rspec, and just .rb as Ruby on Rails:
http://blog.macromates.com/2007/file-type-detection-rspec-rails/
I've just now tried to do the same thing on the work machine, and while it detects rspec, Normal .rb files are coming up as Ruby rather than Ruby on Rails.
The Ruby On Rails language has fileTypes= { 'rxml', 'rb'} as per the blog post (Yes I realize as I type this I need to make it work with Rails 2.0 conventions).
When went looking in the Ruby language def to delete the file type association to 'rb', there doesn't seem to be one.
Any ideas?