Comment 1 for bug 42853

This happens for me too. The only way to "unmute" it again for me is to use my volume up/down from my keyboard and this restores the volume. However... I'm also experiencing another "symptom" -- but not sure if I should file it as a separate bug or not. On my system, with an onboard VIA 8235 (Alsa) AC97 chipset, even when I have the volume slider(s) all the way down and it claims to be "muted," I still receive sound at a very low volume through my speakers. It's not until I actually choose to mute it that the sound stops.