Russ Wenner mentioned a command to get sound working in Ubuntu in his podcast:
Also, you could cut and paste from the terminal instead of taking a snapshot.
I believe the Ubuntu 8.10 uses pulse audio.
The last time I had the audio quit, I ran "killall pulseaudio" and then ran "pulseaudio --start".
It may be better to instead run "pactl" and then enter the command "exit". The press ALT-F2 for the run dialog and enter "pulseaudio --start" which will start the daemon if it isn't already.
I don't use Ubuntu but you may have the same command. The pulse audio device chooser applet is a program called "padevchooser"