I fixed mine about a month ago. The infamous grey/silver gear on the far right had worked loose from the shaft (do a search, this is usually the cause). In my case, the shaft had slid to the left far enough that it fell out of the housing on the right-hand side, causing it to disengage from the gears below it that drive the trip odometer. If the gears aren't all held together, nothing turns.
The fix was simple. Like others on this board have done, I used a small drill bit to push the shaft out and hold the wheels in place. (I wasn't too careful since mine had been out of commission for so long that I had to advance it about 10K to catch up.) I used a pair of pliers to rough-up the spot where the silver gear goes. Then I put it back together and the silver gear fit tightly.
NOTE: The scratches you make in this spot can be barely visible and will still create enough friction to keep the gear in place. I wasn't sure it would work because I could barely tell that I had scratched the shaft. Now I've gone about 1000 miles and it's working like a champ.
Word to the wise - never reset the trip meter while moving -- EVER!
