I've had more than a little trouble with all things GNOMEish in Ubuntu 9.10 since upgrading from 9.04. I've solved all of the issues thus far but discovered another last night. Rhythmbox, which wouldn't even start until I fixed the opencv bug, started but wouldn't play anything. When trying to play an audio file, I kept getting an error message that included this line: "unable to start playback pipeline." That was enough to send me to Google, where I found the bug (#468577) in Launchpad.