Mr. Villain,
can you go into a little more detail how you fixed your problem?
i have a Nokia Lumia 920 as well, my vehicle is a 2011 Ford Flex.
Until yesterday, Ford Sync has been working fine, despite perhaps a little hiccup here and there.
Now i am having the same problem you did - phone connects, ok for incoming and outgoing calls, but music won't play.
I kept telling the system "bluetooth audio" but it replies "no bluetooth device found" (yet no problem for phone calls; BT logo shown on head unit.)
i have deleted Sync from my list of bluetooth devices on the Lumia 920, deleted my Lumia 920 off of my Ford, and then reinstalled both - still not working.
thanks in advance.