Original post by: Majesty ,
Try a SMC reset. This could be any type of hardware failure....it doesn't necessarily mean it's the logic board. I would try disconnecting the Superdrive first, then try booting up that way. You can also try removing and reinserting the RAM sticks. This can also be cause by a faulty I/O Board, and being that you had issues with the USB ports this is most likely the cause.