Just curious, but I had this happen on my '86 shortly after I bought it. Did you happen to push the "reset" button while the car was moving? I don't know how true it is, but I was told by the folks at American Service center,(local dealer) never to do this on an MB as it would jump the odometer off it's track. They quoted an outrageous price to fix it as well, but beleive it or not what worked was simple pushing the reset button again while the car was sitting still. It's been working for 6 years now. Heck what do you have to loose.