It is a surface. It has been offset from an imported IGES model. I am trying to do a surface cut using this surface. I am assuming that the invalid edge is causing it not to work.
Did you do a Diagnose on the surface (if had any) when you first imported it? (You only get this option if don't add anything or do anything to the model when it's first imported)
Did you do a tools\check before working on the model?