I have the navi proffesional with 16:9 screen. My problem only relates to a few commands. Here is a list of commands, and you can see what commands are OK, and which one not responding.
Route map OK
Scale 400 feet/.../Scale 50 miles
OK (but I use meters and kilometers)
Navigation not responding
Gas station at current location/at destination OK
Parking lot at current location/at destination OK
Carpark at current location/at destination OK
Hotel at current location/at destination OK
Restaurant at current location/at destination OK
Save position/Save current position OK
Instruction OK
Instruction off OK
New route not responding
Help navigation not responding (just reads out the help commands for telephone and notepad)