Quite a thread-bump there! 🙂
I'd just like to add - be wary of cleaning your Mighty Mouse too hard, as some suggested above. After vigorously cleaning mine a while back, the ball finally started to move freely. But when I tried to use it, nothing. I must have broken a roller inside the mouse when cleaning it.
If you still have a Mighty Mouse, I'd recommend cleaning it regularly, before it gets stuck, rather than only when a problem happens.