During the Mages Guild quest to get a letter of recommendation, I have to talk to Teekeeus about the book "Fingers of the Mountain". Whenever I try to talk to him about that particular topic, though, the game freezes and crashes. It doesn't crash for any other topic I talk to him about. Anyone know of a fix for this?

Sounds like a corrupted sound file to me. You'll probably have to reinstall or use the console to advance the quest along manually.