This is a bug or some graphical flaw that seems to happen when the flat object is at the 0 position (or flat against the grid). The surface outlines and vertexes seem to vanish (or become hidden) in the 2D view making surface selection (or vertex locating) often a bit of a pain. I've tried the software on a couple of my other computers and it doesn't seem to happen on those devices.
When I move the object from the minimal position the surface outlines actually show themselves again. This isnt the ideal way to work on my 3D models so I was wondering if this was a common problem and if there was a fix. Since I dont have the problem on my other PCs maybe its something to do with this particular PC's graphics settings?
This also seemed to happen in the last version of AC3D 8.6.11 that I had on this machine.