Leaving the unit off for 12 hours does nothing.
When you do a battery pull, how long are you waiting for it to boot before you give up? Wait 15 or 20 minutes. Seriously, someone posted the other day it took 30 minutes for them.
If you've waiting 30 minutes and it is still not finishing, and if you are running OS 4.6 or newer, then see if you can boot in safe mode. KB17877-How to start a BlackBerry smartphone in safe mode
Then, (1) do a full backup, and (2) delete suspect apps, and/or the last one or two apps you installed. If you are using a third-party theme, switch to a stock theme as a test. Then try again. Posted via BlackBerryForums.com Mobile