What it might be? No clue
What to try: One clue.. NOTE: I give you a Money back guarantee on free advice.
Remove the power plug
Remove the battery
Sit on the power switch for one full minute (I think it only takes like 30 seconds but go for a full minute or even two)
Restore battery
Restore power plug
Try again
If it works.. Your choice (This is the expensive part)
A: Buy lottery tickets cause when you hot you hot
B: Do not buy lottery tickets cause you have used up your allotment of luck for the week.
(See how helpful that is)
I have seen it work 3 times. Once was on a DELL.