I've had an AVIC N1 installed for the past few years, working perfectly with the ground hacked so that all system options work while the car is in motion.
I lost the original NAV discs, and upon putting the new ones in, the system software was upgraded. A warning appeared on the screen stating that the system was illegally grounded, and since then the car needs to be completely stopped in order for DVDs to play, and the majority of the NAV features to work.
Any help is much appreciated!