Sorry to hear your troubles. I will look for some answers for you. It didn't get wet or come into contact with a very humid environment like a steamy bathroom? Right off the top of my head, I'm thinking you may have to reset your device. By that, I mean reload back from factory settings with Blackberry Desktop Software. I'll keep looking around for possible causes.
I have searched around the internet for a possible solution to your problem. If this happened to me, I would try to return the Tour for a new one. It sounds like perhaps a defective device. Let me know how this turns out for you. I have a Tour and would like to know.