ha, it muust be frustrating alright, I know the feeling. Ya it doesn't change. It should be playing so.
Try closing mplayer maybe and restarting mpd again? I remember when I was using ubuntu I sometimes had a problem when using rythmbox and trying to play sound with something else at the same time.
Before you try that actually, try "cat /etc/group | grep mpd" and make sure that mpd is listed after audio. Just to make sure mpd is a member of the audio group.
if it's not, try "sudo usermod -a -G audio mpd"