I had a similar problem with my baby-rollei when I got it - it just wound the film straight through. A service sorted it out - didn't cost much (and a changing bag saved the film!).

My Sawyers IV also has a fancy winder mechanism, which is broken, and I suspect my Komaflex is developing a fault. There's a lot to be said for having a little red window at the back - they'll keep working forever (but keep it away from light!).