Force Bake (Invalid Brep)

So I have this geometry that look fine in the preview but it will not bake! It says it's an invalid brep. What does that even mean!?

Rebuilding it with polylines results in something I can bake, but interpolated or nurbs curves make it look so much more pretty :P

Can anyone explain why grasshopper doesn't like my nurbs curved loft? Or how to force bake it into Rhino?