Have you checked the drive belt and tensioner? The drive belts can snap, however they are most likely to stretch. Ride the Mower onto (a low) Brick/s so you can see underneath the cutters (do not, at any time, put your hands or body under there). Get someone to engage the drive and you watch the mechanism move. If the pulleys move but do not engage the belt it either needs adjusting or if at full adjustment, replacing.
G P L, September 2010