I recently upgraded to R5F1, and for some reason the sound has stopped working. I've disabled onboard sound and am using a chaintech av710 for optical out to my receiver, and when I first installed sound worked out of the box. Last night I was fiddling with mythgame and emulators, and now when I run alsamixer it shows my onboard sound chip, even though it is disabled.

Is there any way I can force alsa to ignore this chip, which it should be doing in the first place?

If anyone comes across this problem again, here's a with a solution:
https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/65291

Basically, you set the priority of the cards in /etc/modprobe.d/alsa-base and with any luck your add-in card becomes the primary.