Should have installed the "IneffectivePower" tweak. Karen (AKA angelXwind) uploaded a fix for this a couple days after it was reported. Try holding the "up volume button" while it boots up to see if you can get to the lock screen. If you can get to the lock screen, look in the news forum to see if any of the suggested temp fixes help restores your messages. If the temp fix works, install IneffectivePower right away.