Your not alone man, I just had the same issue and come to found out it is the motherboard. Sorry to say you may have the same issue. Some people say to bake the motherboard for like 5 min in a oven which I wouldn't recommend. Your best best is to try to do a hard reset by taking the battery out and hold down the power button for 30 seconds. If this some how happen to work for you for a short time I recommend you back up your files while you can and then just say good bye to it. I thought about just getting a new motherboard but it's risky getting a new one that works good with out it breaking down on your weeks later. I was luck to back up the files I needed just in case, but over all I'm force to get a new system soon. Sorry man, it may just be the motherboard.
Kolumbo
well god damn it fornoreason, what's next? your commodore64?
ForNoReason
My Atari 2600 just spontaneously combusted :(