There is a recorded problem with the tulip driver in the kernel shipped with Ubuntu 6.06. The 'tulip' driver claims the card, but it should be assigned to the 'dmfe' driver.
This problem was fixed in the package for 2.6.15-24.40, and the latest kernel from dapper-security should no longer have this bug.
sudo -s -H rmmod tulip rmmod dmfe modprobe dmfe /etc/init.d/networking stop /etc/init.d/networking start
Add dmfe to /etc/modules and add blacklist tulip to /etc/modprobe.d/blacklist, such as by issuing the following commands:
sudo sh -c 'echo dmfe >> /etc/modules' sudo sh -c 'echo blacklist tulip >> /etc/modprobe.d/blacklist'
apt-get install alsa-oss