Re: GRRRRRR....broken drive sprocket....
It sounds like your wheel works something like a freewheel hub on a bicycle. If it is turning in both directions without grabbing then there is probably something broken in the hub. I'm not familiar with your type of ride so I can only guess. Have you taken the hub apart to inspect it? Bits of metal on the inside would be a sure sign. Good luck!
If it can't be broken I'll find a way!
I'm not lost, I'm exploring!