Yesterday drove down to the West Midlands - navigation working - on my way back it froze, then it wouldn't show the map screen or direction screen, audio still working on CD and radio. Then the screen changed colour and I got a service screen mode up and a lot more menus were available. On the start up screen navigation had disappeared and was replaced with the OBC (On Board Computer) computer settings which are not available on the V8 due to the gateway ECU (Engine Control Unit), lo and behold now could switch on and off the TP function. This continued until I arrived home, I had pulled off into a services and switched of the ignition and then restarted to see if that cleared the problem, but it didn't. A couple of hours later I tried it again and everything back to normal and today I've used the navigation and alls working as it should - spooky or what.