I found this post useful and important to share, so if anybody has problems running textmate after updating to OSX lion, do as follows...
[from http://thelucid.com/2011/11/24/textmate-refusing-to-launch-in-lion/]:
On occasion under OSX Lion, TextMate refuses to launch. I’ve found that simply deleting it’s pid file seems to get things working again, just open Terminal and type:
rm ~/Library/Application\ Support/TextMate/TextMate.pid