That's weird. Any errors in /var/log/messages? or /var/log/boot.log? Do you know if the system has configured the correct chipset for you, maybe it didn't recognize it?
It looks like 2006 runs alsa 1.0.9, there have been a few fixes for ali5 modules (turning off DRA since it's not supported, etc..), as well as lots of fixes in non-chipset-specific areas, so you could try to update it (urpmi --keep FILENAME should work):
http://www.alsa-project.org/