Frank, the link JerryG gave is a good one, and tells exacatly how to correct the problem. Mine got stuck several years ago, and I freed it up. I was also nervous about putting too much pressure on the gears and breaking something else.
It takes a good size screw driver, or pry bar. It also took some trial and error - it's hard to see in that little access hole. Finally out of desperation, I gave it a good shove, and the gear moved where it was supposed to be. Have never had the problem since.
Good luck, and let us know if you get it fixed.