Comment 16 for bug 80893

I not only did a cold reboot, I even unplugged the MB for >1h before restarting 2.6.20-11 generic -- but no sound.

Restarting 2.6.20-10-generic did give sound!

Looking with Kinfocenter under Sound I found these differences:
-10: (with sound)
Audio devices: HDA Generic
Mixers: Realtek ID862

-11: (no sound)
Audio devices: ALC861VD Analog (Duplex)
Mixers: Realtek ALC861VD

I noticed another difference between the two kernels: My cheap loudspeaker system hums noticeably when unplugged, which still continues when plugged into the switched-off motherboard, but goes away during hardware detection at boot. So when suspending under -10 and -11 the humming restarts when the MB is completely suspended. The difference is that at resume with -10 the humming remains, while at -11 the humming goes away immediately.

Electrically this indicates that during hardware activation the circuitry is going from an "open" (=humming) to a "closed" state (=no humming). This is also correctly happening during resume in -11, but not in -10. In this regard earlier kernels behaved the same as -10 (so at least something promising ;-) )