01-31-2013 03:48 PM
Yank your battery out while your phone is powered on then replace it. That will solve the issue in most cases. If your phone is really being stubborn and that doesn't do it, chances are it's a hardware issue with which we can't help you here; you'd have to take it in for repair.
If the battery pull doesn't work and you want to throw an extra step in there before taking it for repairs, you can also try reloading the OS using BlackBerry Desktop Software.
Keep us up to date on your progress.