OH i see. well on my sat nav disc it says GS, LS, IS but mines the older CD based system, but im guessing the same applies. So youve pin pointed the problem to be the DVD drive in the boot? It could be either the laser, the motor that moves the laser, the motor that spins the disc or even just a loose connection Not sure about toyota prius if it would work, if so what about an avensis alot of them had nav. hopefully someone will advise