Try starting rhythmbox from a terminal and attaching the log. I would also recommend you try playing the same files with totem to see if it is an issue with rhythmbox specifically or something deeper (like gstreamer or pulseaudio).
Try starting rhythmbox from a terminal and attaching the log. I would also recommend you try playing the same files with totem to see if it is an issue with rhythmbox specifically or something deeper (like gstreamer or pulseaudio).