My mower was making a clunking noise when I changed directions with the pedal, kind of like a really badly worn u-joint in a car. Then it started barely moving forward or backward. Finally, it stopped moving altogether. As it turns out, the drive belt has come off of the transmission pulley and the rear wheels only turn in opposite directions. They also will not free-wheel with the trans disengaging pin pulled in the back. Is all of this simply due to the drive belt coming off? This machine only has about 150 hours. Is it typical for the belt to need replacing this soon. Any other thoughts would be greatly appreciated.