Comment 10 for bug 391114

I've filed a bug report today with a similar problem:

https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/434511

Although playback works for me most of the time (sometimes I had only background buzz and no sound at all), the mic only works when I'm recording from within a live session (using the 9.04 and 9.10 CDs). Maybe you could try that too and see if it makes a difference...