See if you can boot in safe mode. KB17877-How to start a BlackBerry smartphone in Safe Mode
If you can boot in safe mode, delete the app and then do a hard reset (battery pull).
If you can't boot in safe mode or deleting the app doesn't fix the problem, see the following link at the FAQ. Is your BlackBerry Nuked? - BlackBerryFAQ Posted via BlackBerryForums.com Mobile