Mario Carrion
Due some patent issues, playing mp3 requires installing some extra packages. Ubuntu 'Dapper' needs them, you need to install the gstreamer-0.10 plugins.
# apt-get install gstreamer0.10-plugins-ugly gstreamer0.10-plugins-good gstreamer0.10-plugins-base gstreamer0.10-plugins-ugly-multiverse
Does the trick.
BTW. GNOME 2.13.91, runs better, faster and smoother. Quite impressive.