I don't think there is a "belt" in the seatback drive system. From what I remember (its been a few years) there's just the drive-cable coming out of the motor and it attaches to the drive gear on the left back side of the seatback with a shaft going over to the right seatback side gear. Sounds like either the shaft detached or the plastic gear on the right side is stripped or jammed. You'll need to pull the rear of the seatback up and examine the drive pieces. There's a procedure for this over on Bay-13 at VolvoSpeed.com (look under misc. repairs, seatback cable replacement). You may find it easier to pull the seat out of the car to work on it, but thats not too hard. Maybe its just easier to try and find one at a junkyard that matches your interior color, they should be readily available. Good luck ........ Mike