Comment 3 for bug 639846

The kernel you are currently running is from the proposed updates repository. Why you have that enabled I don't know, but the proposed updates repository is used for testing possible updates to be released into the updates repository for all to use. Unless you need to test a package from that repository, Isuggest you disable it from the software sources preferences.

To test a possible solution, I suggest you install the following packages:

linux-image-2.6.32-25-generic
linux-backports-modules-alsa-2.6.32-25-generic
linux-backports-modules-alsa-generic
linux-headers-2.6.32-25-generic
linux-headers-2.6.32-25

Also make sure you have the package linux-image-2.6.32-24-generic installed, so you have a tested and released kernel to reboot into.

Once done, I suggest you update your alsa drivers as outlined here: https://wiki.ubuntu.com/Audio/InstallingLinuxAlsaDriverModules. Note that the latest version of this package is available only for kernel 2.6.32-24-generic.

Please report back whether these alsa updates I suggested help resolve your issue.

 affects ubuntu/alsa-driver
 status incomplete