OK, so everything was fine this morning, I was listetning to music, watching videos - no problems. Just about half an hour ago I go upstairs to have lunch, closing the lid and putting the MBP to sleep before doing so. I come back after lunch, open the lid, and try watching a video on youtube...no sound. I unmute the sound on the youtube video player and check the sound slider...still no sound. I then check the sound on the actual computer...It's on full and no headpones are plugged in...and yet still no sound. I do further checking by playing music in iTunes and opening some Quicktime videos...still no sound. WTF??? I then restart the computer, and boot into Apple Hardware Test, run an extensive test and it finds no problems. The strangest thing is that the keyboard sound buttons (F4 and F5) don't seem to respond while the mute button (F3) does respond but doesn't do anything (and by respond I mean the little transparent thing that pops up). I then check system Profiler and in the built-in Audio section, it says I have NO BUILT-IN audio! So what the hell is happening here!? Please help!!!