fireworm make sure you're editing that in sudo as administrator

also,
i had the same problem and i don't know where the thread is nor the full solution (though there is a thread on it in ubuntuforums).. it definitely is something to do with pulse audio. i had to install the pulse audio engine and device chooser and run that panel applet on each startup.. and make sure all the devices under system-pref-sounds were set to pulseaudio.

hope thats of at least a little help.