I felt like I was falling forwards as well when I first ran (it is pretty frightening) I tripped on about my 3rd run and ended up going way to fast to recover
Try to jog on the spot and then go forward a couple of steps and then stop again
Stopping is an aqquired art I use to just try and slow down and it took me about 6-8 strides but now I sort of backpeddle (hard to discribe watch people on the vid and you'll see how they seem to lean back and jog)
anyway good luck with it and above all keep trying