Alright, this one is odd, but it works like a charm. I recently installed Safari 3.1 on my new MacBook and after a reboot I had no audio whatsoever (though the startup chime worked). When I messed with the sound via the keyboard buttons only a greyed out icon and a barred circle appeared. I also noticed a red LED inside my headphone jack (what the hell?)
Googling around I found a super weird fix here.
The fix is to get a toothpick and stick it all the way into your headphone jack roll it around the edge of the jack until the light goes off. Yeah. I know. It really works though. I swear.
My audio was working again immediately without a reboot!
