Comment 71 for bug 25896

"Me too." I'm running Hardy Heron, though I had this problem with Gutsy, as well.

One thing of note, Hardy uses the PulseAudio sound server by default instead of ALSA. But I believe it pipes ALSA through PulseAudio. Because Hardy uses PulseAudio, there's a different workaround available. From a terminal, run:

sudo killall pulseaudio
pulseaudio &

This completely kills the PulseAudio server, then restarts it. The '&' allows you to close the terminal window without causing PulseAudio to be killed as a side effect. This is about the same as the ALSA method, but it seems "cleaner" since you're working only with a program instead of a driver module.

You will need to close and restart any programs that are actively using audio; they'll become very unstable and likely crash on their own otherwise.