It's a Crankcase Stud Updated. Go check it out for the details. Sounds like something everyone should do.

 

Sounds familiar,

I've got mine in the shop for this right now. It's the plate that holds the tranny to the main engine case. Mine came loose and tore some stuff up. Cannondale warranty. We have two of them and there replacing on both.[img]i/expressions/face-icon-small-sad.gif[/img]