I've got a part I've created and am having trouble with a surface on the part. It's showing up as clear or transparent. The surface is not set to be transparent nor is the material/appearance set to something which is clear. I've attached the part picture below.  The part was created with typical cut, extrude, etc. type features.  It was not done with any surfacing.

Anybody seen this before and/or have a work around?

Thanks!

Matt