My girlfriends 2010 Macbook Air (Core 2 Duo one with 320m) had its sound completely stop working. The volume controls are greyed out and there is nothing listed under output devices. I tried resetting the PRAM, SMC, and even updated it to mavericks and no luck. This happened one time before and resetting the PRAM fixed the problem. It doesn't matter if headphones are plugged in or not, the volume control is always grey, and when I try to change it via the keyboard, a greyed out speaker icon just pops up. Any idea? Its out of warranty, so taking it to apple would end up costing the $300ish flat rate repair fee. I just want to see if theres anything I can try before ending up having to pay that cost.