@blowfish: I had the exact same issue as you had. All of a sudden the sound did not work anymore. So, actually I reinstalled alsa, using
Rebooted, and still no sound. I got agitated, turned the laptop off and went to sleep. This morning I started the laptop again and the sound was back.
sudo aptitude reinstall alsa-base
So to be honest, it looks more or less random whether or not we have sound . You could try reinstalling the alsa base.
Oh, also verify if in your BIOS (somewhere around something called security, you can set pci locks) that the soundcard is set to unlock. That's all I did, and now I have sound again .