See if you boot in safe mode. See the following link, if it is still good, or search. KB17877-How to start a BlackBerry smartphone in Safe Mode
If you can boot in safe mode, delete the app. If the device doesn't restart, do a battery pull. See what happens when the device reboots.
If that doesn't work, see blackberryfaq.com and the article on what to do if BlackBerry is stuck in a rebooting loop. Posted via BlackBerryForums.com Mobile