Just a thought --- the Garmin system (aftermarket system) I have requires loading in the area you wish to drive thru in order to have the highly detailed maps. If you drive out of the area you only have a "base map" with not much detail of secondary roads or street level.

Did you purchase the ML500 from an entirely different area of the US ? Perhaps you were not given all the 9 disks needed ?

Most likely a call to any MB dealer could help.

DanielW