Comment 7 for bug 992303

I have Ubuntu 12.04 64Bit via an upgrade from 10.04 I think. Anyway, i had the same issue.

To resolve it, after much messing on, I did this

Sound Settings ( Via the wee speaker in the top panel ) -> Output -> Speakers ( Built In Audio ) -> Mode:

It was set to Analog Stereo DUPLEX.

I changed this to

Analog Surround 4.0 Output

And all my music came back on.

Just so you know.
Peace.
Dunk
http://www.realityinfo.org