I have had my iPhone 3GS for a few months without any problems. All the sudden yesterday I charged the phone but after a few hours the battery had run out. I charged it again today and the same has happened again. I have tried to reset the phone but it is still doing the same thing. It seems to be running something because the back of the phone is warm as well. Anyone got any ideas on what might be draining the battery or what I can do to stop it?