A few years ago I had a client with an identical issue. Unfortunately, we ended up having to replace the AAM (All Activity Module), ME-SFI (engine management module), and the entire vehicle lock set. According to MBUSA, there were no other options. The owner had recently bought the vehicle (an ML) from a used car dealer, who only supplied one key. When that key failed they came to my dealership to order a replacement. That's when the nightmare began. They had to spend a few thousand dollars so that the car could be driven! After we made the repairs, they promptly sold the car to the first person who made an offer. They didn't want any more surprises. Welcome to the wonderful world of MB!!!

Hey Rob, I'd recommend calling MB's Customer Assistance Center at 1-800-FOR-MERCEDES. Ask if they can find out for certain that all the keys for your vehicle have been used. Also inquire whether or not a solution to this problem has been considered. I'm sure you're not the only person who has been in this situation. MB is pretty good about looking into problems if enough people complain. Let us know what happens.