I think Mark is correct. What Eddie describes is similar to the X-29, forward swept wing. The wing would just rip off, not flutter.

I seemed to remember hearing that the thickness of the ailerons on CAI stuff did not match the TE of the wing. If the control surface is thinner then the wing, doesn't this excite flutter? Probably one side started to flutter first, and the vibrations kicked the other one into flutter.

Just a thought..