Ok...you guys have been extremely helpful. I will follow all of your suggestions and see what happens. I definetly have an SQ 120 back. The red light goes off after each trip of the shutter, so that's good news. I'm going to put another roll of film through and watch the crank. I can manually crank it and the number does move, it just doesn't move with the shutter or when I press the motor drive, although I can hear the motor drive and it sounds like it's working properly.
I truly appreciate your help!
Nancy