You will find it working when you have left the car switched off for a bit.
This has happened to me also on my Discover Pro Radio last week. Today the SAT NAV map froze mid 3 hour trip

but oddly the verbal directions and the distance/time left carried on with no bother and everything else was working.
I have found that if you press and hold in the power knob for a few seconds the unit will do a soft reset (You get the VW Logo and Starting Navigation Screen) and all will be working again but it does forget the last destination and goes back to the Media track that was playing when the car was first started (SD Card in use).
It sounds like a software/firmware fix required, I'm on currently on Version 0192