I haven't read all the replies but you need to do an “SMU reset" the way to do this varies on every machine so Google that with your machine info and you should be good to go. Also doanother pram reset if you haven't (after the SMU) and then make sure it's all charged up before shutting down again (if it's a laptop). Hope this helps. It should. I've had this happen. Its pretty common. I'm sure most peeps here have had this happen at least once. Cheers