I'm having similar issues every so often the sound just says no for 15 to 20 seconds. It seems like every now and then the audio controller just "runs out of memory" freezes up and then comes back. I can tell you, with certainty, that it is not my headphones as one time I was talking with a friend during a "mute-out" and I could still hear him talking clearly. I haven't paid enough attention to remember if it happens during particularly busy times, but I'm pretty sure it has happened while I'm just riding around by myself.

This is the first forum post I've found from recent enough, and similar enough to my situation, to be relevant. I hope something comes of this; while this isn't game breaking it is very annoying.