If you are having sound issues with Enemy Territory, i.e. you don’t hear anything, you might want to try this:
$ sudo -i
$ echo "et.x86 0 0 direct" > /proc/asound/card0/pcm0p/oss
Worked for me on Ubuntu Gutsy.
You can find more help here.
UPDATE: Still necessary and working with Ubuntu 8.10 Intrepid.