Googled it and came up with this:
It could be a lot of issues of why this is happening.
1. Try updating your video card.
2. Your computer hardware may be insufficient to run it, or damaged.
3. Try doing a reinstall of TF2, in case some files are corrupted.
Try joining a game that someone else is in, which would completely bypass the menu to find servers. If that works and things look fine then it could be some files with the menu.
Try submitting a troubleshooting request on the Steampowered forums for assistance if this keeps going.
Subject: HELP TF2 
Mon Jun 14, 2010 8:59 am
