Michael,

This is probably just a surface edge. Don´t worry. I justed needed an excuse to post a picture of my catamaran :-)

The "trimming bug" previously mensioned in this thread is definitely some kind of a "kink" Prosurf, not MoI.
Here are some pictures of what the .dxf mesh generated by Prosurf looks like and as a comparison we have the .dxf mesh
generated by Rhino.