Here is what I would do. First hold down the power button until the device shuts off (or reboots). If it shuts off, turn it on again and test. Test once the PlayBook boots up.
If that didn't work, do a security wipe. Test. If all is well, restore your data, except calendar and messages. Test. Decide whether you want to risk restoring calendar. Of course if you don't have backup this is moot.
Worst case, reload the OS. Posted via BlackBerryForums.com Mobile