I was attempting to do a very simple copy with mates on a part where it had three mates, all three being coincident to surface.  I checked repeat on two of the mates with no issues.  When I tried to click on the third surface to mate it was covered by the part I was copying.  When I tried to slide the part to be copied out of the way, it would not move.  When I hovered over the surface, right-clicked and selected other, I could not get the face of the surface to highlight.  This has never been an issue until now and we use "Copy With Mates" a LOT!  Has anyone else experienced this glitch?  If so, can you tell me how to remedy the problem?  Thanks, everyone.