Comment 146 for bug 80893

One more bug to check for workarounds:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/270593

"logging out, (killing pulse-audio) followed by alsa force-reload
re-instates sound."

I'd also try suspend/resume by starting Ubuntu 9.10 from the liveCD
(installation cd). That's how you can check if some config file from
older releases causes the problem. I previously had that problem but I
cannot remember how I fixed the problem (reinstalling acpid ,
acpi-support, alsa-base or something like that).