Intel DH67BL and Ubuntu Oneiric: Audio problems

[^rooker]

[PROBLEM]
I've experienced a very, very weird behavior of my sound output when running Ubuntu Oneiric (11.10):
The rear audio output turned itself off every once in a while. It only worked about 5 minutes per hour or so... hmpf.
When the problem appeared, the volume faders started trembling (no matter in which application: From XFCE's Mixer to Alsaconf - and even the volume indicator plugin), and the mute state was flickering on/off.

Scary...

I first suspected a hardware problem, but then I plugged earphones into the front audio out, and interesting:
The front audio worked all the time!

Another interesting thing:
The problems started after enabling the front audio in the BIOS. I've currently set it to "Legacy" (instead of "Auto" or "High Definition".

[SOLUTION]
One solution is probably to disable the front audio panel in the BIOS, but I've figured out a weird behavior-connection between audio channels which currently seems to enable me to re-enable the rear output:

The "Headphone" output!

Togging mute/unmute of the Headphone output in XFCE's mixer (or alsamixer) suddenly turned the rear-audio back on.
However, there's a small inconsistency:
When unmuting Master and Headphone in XFCE's mixer (Device: HDA Intel PCH (Alsa mixer)), it's not enough:
The volume indicator plugin still showed the master being mute. I've clicked the indicator plugin, selected "unmute" and the sound was back.
Weird...

Additionally:
Unmuting in alsamixer (or XFCE's mixer is not enough), *but* turning the volume up to the max of Master and Headphone, actually unmuted it.