My wife was driving home from shopping and noticed an accumulation of dust on the rear window. She used the rear wiper to clean it but it came right back, she repeated twice and gave up. Approx 3-4 miles later she heard a POP and red lights came on the dash, when she pulled over ASAP in a safe spot smoke started coming from under the hood. She shut the engine off and tried to exit the car to find the hood release under the dash but there was fire coming out from under the car. She closed the door, grabbed her purse and cell phone and got out quickly as possible, burning her ankle and singing her long skirt. She got approx 50 feet away, looked back and the entire car was ablaze, centered mid vehicle, as well as 4-5 spot fires along the road she had just traveled. Previous to the POP the car was driving, steering, and braking normally, no warning lights of any kind. Visiting the site the next day revealed sound deadening/insulation material in and along side the roadway for 2-300 yards as well as dripping molten aluminum, corresponding to the area traveled after she first heard the POP. The vehicle had extensive repairs of cascading failing emissions system components only 7-9 months earlier, culminating with 42 days at Mercedes San Rafael where one component after another failed and was replaced. Myself and all knowledgeable persons i talk to assume it was an overheated catalytic converter that caused the problem. So far Mercedes has not been aggressive i trying to determine