I have had this problem with my E-320 2000 when I first purchased the car, I thought is was just a bulb to my dismay, I was informed that the instrument cluster was failing and needed to be replaced. It cost almost 1k, to fix, the dealer gave me the runaround and I almost ended up taking them to court; but didn't want to go through the head ache..... to make a long story short they agreed to pay for half the cost; because the warrenty I purchased with the car did not cover it.
The plot thickens after mercedes took the car to repair it they told me the instument cluster had to come from germany and the last documented milage the had on the vehicle was the milage when I first purchased the car 58,200 I had already put about 2 to 3k on it before I had the cluster change.. When I received the car back it had the origenal milage that was on the car when I first purchased it 58,200 so my car really has about 2,500 more than the milage says! I dont know if thats good or bad!