I recently upgraded my work PC to Ubuntu 9.10 and in doing so lost the ability to play mp3s in Rhythmbox. When trying to play an mp3, rhythmbox would ask for a new plugin, but after looking, say it couldn’t find “GStreamer element autoaudiosink”.
After reinstalling gstreamer and rhythmbox a few times I turned to the Ubuntu Forums. The answer is in the following thread, but I missed it on first glance so thought I’d post it here: [ubuntu] rhythmbox 9.10 mp3
To save you reading through all the posts, to fix the problem after upgrading to 9.10 (not from a clean install), you need to delete your gstream preferences. Open up the terminal and type the following:
rm -rf ~/.gconf/system/gstreamer
rm -rf ~/.gstreamer-0.10
If you log off and back on again now, you should have mp3 playback in rhythmbox again. If that doesn’t work, take a look at the other suggestions in the ubuntu forum thread.