I was dual boxing, and found I had no sound on one account entirely, and only the GM Voice on the other. Next time I logged in, had nothing, not on any account, not even the dramatic intro music on the character selection screen. Could still hear Player Voice comments in game, tho'.
Rebooted, ran "fix errours", been a couple days of off and on playing - nuthin'. Tough to hear when you run out of ammo when you can't hear anything.
I'm guessing the sound files have been corrupted??? Reload? (Hate to do it, soooo slow on my machine.)
~Any~ other suggestions?