If the belt is ok, then it may be as mine was. Where the belt pulley is, there is a shaft that goes into the top of the transaxle. On the end of this shaft is a gear. This shaft and gear is removed by taking out three 10 mm bolts. The gear on the end of this shaft mates to another gear on a cross shaft held within the transaxle. That cross shaft has a spline that drives the gear which inturn is driven by the gear on the shaft attached to the belt pulley. Unfortunately, the spline wears and can fail to drive the gear. The transaxle has to be removed and split open to replace the cross shaft. Not a terribly difficult operation if you are halfway mechanically minded like myself.
Paul, May 2010