I had the same issue until I played with the alsa settings and now I have no sound at all (speakers are not muted).
The fix James reported doesn't apply as the line referenced in the article does not exist in my alsa-base.conf.
The problem started when the computer was still running 10.10 - this weekend I upgraded to 12.04 (multiple upgrades), with the final upgrade to 12.04 failing, leaving the computer in an inoperable state.
Reinstalled 12.04 from the Live CD and restored home folder - sound problem was not affected by the upgrade.
I had the same issue until I played with the alsa settings and now I have no sound at all (speakers are not muted).
The fix James reported doesn't apply as the line referenced in the article does not exist in my alsa-base.conf.
The problem started when the computer was still running 10.10 - this weekend I upgraded to 12.04 (multiple upgrades), with the final upgrade to 12.04 failing, leaving the computer in an inoperable state.
Reinstalled 12.04 from the Live CD and restored home folder - sound problem was not affected by the upgrade.