Comment 17 for bug 272960

I've found a fresh install of 9.10 (or alternatively, booting from liveCD) works Fine & Dandy on the external speakers. There appears to be a bit of a problem with the headphone jack, in that as soon as you plug in headphones, you can hear a split-second of sound (through the headphones), before both headphones & External speakers are muted.

Any ideas?

More info, including bash outputs here:
http://ubuntuforums.org/showthread.php?t=1333532