[TxMt] Errors running Ruby in Textmate

I have started making use of the 'Run Script' feature for ruby files I'm editing. All works fine and then I start to get this error: /Applications/Tools/TextMate/TextMate.app/Contents/SharedSupport/Bundles/Ruby.tm bundle/Support/tmruby.rb:115:in `sub': wrong argument type nil (expected Regexp) (TypeError) from /Applications/Tools/TextMate/TextMate.app/Contents/SharedSupport/Bundles/Ruby.tm bundle/Support/tmruby.rb:115

Quitting and restarting TM bypasses the problem, but it would be good to have it fixed! I'm on OS X 10.4.5, I'm willing to provide more info if that helps...

Thanks in advance - Jonathan