One more thing: when the Mk3 gets in an endless loop after inserting a Mode1 CD, it stops talking on the I-Bus.

So you cannot reset the language using the DIS. The dealer will tell you the nav unit is faulty. But it is not.

You must eject the Mode1 CD, then you can insert a Mode2/Form1 OS CD and the nav unit will boot up, load the SW and come back to life.

I know, because when it happened to me, I was monitoring the I-Bus with my PC and saw everything happening.... scared me to for 30min, but I recovered OK :-)