This has happened to me a few times also, it hurts like a son of a bitch. When you go over the handle bars, you smash your noggin and shoulder at the same time. The first time I did it, I saw stars, I thought that was just a myth, but I really saw stars. It feels like someone grabbed you by the legs kinda like a baseball bat and swung you around to hit the ground as hard as they could. It has happend on my 167 rossi alpine and my 188 coiler PR, and usually when I am going pretty fast. By reading Bordy's thread about detuning, it made sense that it will reduce nose loading, and come to think of it, all the times it happend, my boards werent detuned.
Cya
Jason