Установите gstreamer0.10-fluendo-mp3
sudo apt-get install gstreamer0.10-fluendo-mp3
и:
sudo apt-get install gstreamer0.10-plugins-bad
sudo apt-get install gstreamer0.10-plugins-bad-multiverse
sudo apt-get install gstreamer0.10-plugins-base
sudo apt-get install gstreamer0.10-plugins-good
sudo apt-get install gstreamer0.10-plugins-ugly