Washer agitates, but does not spin

I have an Amana top-load washer. The pump is directly driven off of the motor, and there is a single drive belt to operate the drum. The machine recently stopped spinning and agitating, though we could still hear the motor running. I assumed that the washer had been overloaded and the belt broke. When I opened the washer, the belt was indeed glazed and broken. I replaced the belt. Now the washer agitates, but the drum seems to "seize" up when the washer gets to the spin cycle, and the motor pulley spins against the belt, which is apparently what happened to cause the belt to fail in the first place. Is this a transmission problem, or a brake problem? How do I diagnose this further, and which part is mostly likely to need replacement? The model number is ALW480DAW.