I was using my laptop, and it suddenly powered off by itself. It wouldn't start back up for about 10 minutes, then somehow it turned back on. Everything works on the laptop, except sound. There is no startup tone, but when I press the volume adjustment keyes, it responds just the way it does normally (no strike through on the speaker symbol). I don't see any red light coming through the speaker jacks, and the hardware test says that there are no problems. Any help is appreciated!