You may have some thread, hair, or other material wrapped around the spindle of the roller. With a new belt it still may not move, so the belt spins, heats up and burns through.
With the vacuum UNPLUGGED, there should be a way to unclip or unfasten the roller, remove it and clear whatever material around the spindle is causing it to foul (not turn). If the motor starts and runs enough to cause the belt to break, the cause is almost certainly on the roller.
Kerry, February 2006
