Just upgraded to Ubuntu 9.10 (Karmic Koala) and am having sound issues like many others.

Changing the system tray volume control doesn't affect the speaker volume at all, until I set it to 30% or below, at which point the speakers completely stop producing any sound
Using gnome-alsamixer, watched what happens when I lower volume: until the threshold, Master is dropping, then at that 30% point (when Master hits 0), PCM and LFE begin to drop. At volume control 0, all three of them are at 0.
Checked ALSA drivers (up to date), deleted and reinstalled PulseAudio (no change at any point in the process)
Curiously, the minimum volume threshold is still there when I plug in headphones (through the headphone jack), but the volume control changes the sound output; gnome-alsamixer continues to do the exact same things as described above.

I will be happy to provide specs or run diagnostics if needed. My soundcard is a Sigmatel STAC9200 and I'm running Karmic on a Dell Inspiron notebook.