Roto Belt

What's wrong with my roto-tiller?
So I just bought a house and borrowed my wife's grandpa's roto-tiller so I can finally plant the garden I've always wanted. I was in the middle of tilling the plot when the tines just stopped turning. I turned the tiller off and saw that the belt had come off so I removed the cover and put that back on, but still no luck. It fires up no problem, but the pulley that comes out of the engine and turns the belt isn't turning. Does anyone know what happened and how hard/expensive it will be to repair?
Kyle's answer made me remember - I was able to turn with my hand the pulley that come out of the engine, the one that actually turns the belt and thus the other pulleys. If it were jammed would I be able to do that?
Drefuss is correct. It is an easy five minute fix.
1972 Canadian Belt Drive Kenmore Washer