I did a search trying to find a similar problem, but I cant find anything. Just a few days ago, I've had a problem with my mbp and the built in speakers. Randomly the speakers won't play any sound, even after turning up and down all the way and muting and unmuting. The only thing that seems to work is plugging in headphones and then unplugging. Im running 10.5.2. I also have the sleep problem 25% of the time, where it will not wake up from sleep and the dvd drive makes a loading sound and the screen remains black.