I was driving this mower and it just stopped moving... while driving. Engine runs and blades engage. Tow rod is pushed in and attached to the lever on the transmission. Belt is not broken, has not slipped off pulleys, and appears to be proper tension. Brake is not engaged. There are no foreign objects preventing the free flow of the forward/reverse pedal or rod that attaches from the pedal to the transmission... and it is still attached. Same for the brake pedal... everything is attached normally and no foreign objects. The rear wheels have never been removed, so I don't see the locking pin as an issue. I am completely stumped.

Check the pulley on top of the tranny , I have seen several of these strip insde and not turn the transmission shaft , and it happens like BANG! Stops and nothing.
Luck

Thanks for the reply DG. When the forward/reverse pedal is depressed, the belt stays motionless. If the pulley on top of the transmission assembly was stripped inside and not turning the transmission shaft, wouldn't the belt still rotate through the pulleys? I am getting no belt movement when I depress the drive pedal. Am I missing the point here, or could it be something else? Thanks