Hey guys -- I've had an issue with two different 3GS's. I recently had to sell my 4, and two of my friends have let me borrow their 3GS's. They both have the same issue. They shut down randomly, turn back on, and then shut down again without letting me do anything. If I plug the device into power, it will boot up and I can use it just fine. If I unplug it, it'll last until it decides to shut down. Both devices worked fine in iOS 5. What's the problem?? Thanks in advance.