Yesterday I was playing music with the raspyfi connected using a wifi dongle to my PC. While playing music my wife turned off the PC and after turning it back on I had my connection back but the webGUI was gone and I couldn't get it back up. I had to reboot my pie to fix it.
I think MPD went down because I couldn't reboot it:

sudo /etc/init.d/mpd restart
[ ok ] Stopping Music Player Daemon: mpd.
[....] Starting Music Player Daemon: mpdFailed to bind to '[::]:6600': Address already in use
failed!

Because I'm new to Linux (started this weekend) I was curious if I can unbind this port and get mpd connected again.