Happened to my w124 260e a few months back.. did the same thing, pushed the reset button and the odometer stopped working for a day.. noticed though that the counter some what got mis aligned and clicks when running..
What i did was take out the panel and dis assembled it.. inside i saw that the gear connected to the counter had slipped from its place and is not in contact with the other gear at the bottom portion. pushed it in back in place and now its working fine..
Try it, might be the same fix for your problem..
