Comment 8 for bug 394282

I finally got everything to work.
Here's the recipe.

sudo apt-get --purge remove linux-sound-base alsa-base alsa-utils alsa-source pulseaudio
sudo apt-get install build-essential linux-headers-$(uname -r) module-assistant alsa-source
sudo dpkg-reconfigure alsa-source
sudo module-assistant a-i alsa-source
reboot

Works.
This leads me to suspect that there is some small inconsistency in code between the current rt kernel and alsa, or that the upgrade to the current rt kernel was not handled properly.

If no one else says that this bug bothered them, or if some time elapses, this bug should be closed out.