After reboot from AVG, noticed I had no sound
You also may want to see what's in your AVG quarantine folder, since this event took place as you described. There's always the chance that something to do with your sound as quarantined as a false positive, these things, though rare to this extreme, can happen.
There was a question that I asked earlier, maybe it was overlooked. Did you run whatever one-time system cleanup utility that AVG offers? If so, there should be a chance (was when I last used AVG), an option in the menu, to restore anything that was changed. These utilities often does more good than harm. My advice to you, if you do get this going again, is to remove AVG & not look back, though I probably don't have to suggest this. But unless reinstalling, don't remove it yet, as what you need may be somewhere in the quarantine or system utility cleanup folder.
This topic will serve me as another reason not to touch AVG again. It's a shame to install security, thinking it's going to protect you, then get screwed like this. You should also let the folks at AVG know about this incident.