My guess is that these parts were started as solid extrusions and later converted to sheetmetal parts. From within an assembly I could neither Edit >> Component Operations >> Cut Out nor Edit >> Component Operations >> Merge using these parts. Pro/E would report back that these parts were 'invalid selections'. I finally ended up remodeling the parts to solve the problem. But now that I have the cut out working, I have a different problem, which is neither Gambit, EnSight nor CFdeisgn will read in the geometry so I can begin meshing.