Blender error- random transparent faces on mesh?

[AlbertKermin]

I have been working on my first mod for a while now, and I'm rather stumped on something. I've tried to find any tutorials I can, but none of them seem to explain what is causing this error, or how to correct it.

Namely, with my UV textures, one or two faces of an object will randomly make themselves transparent when viewed in texture view or with Unity (or in KSP, for that matter!). The transparent face appear normal when rendered, however.

The entire part is one object, and there is only one material/texture for the whole thing.

A prime example is the munar surface retro-reflector I've been trying to build :

What am I doing wrong, and how do I correct it?

[SpannerMonkey(smce)]

It looks to me that the uv's are simply on the wrong side of the poly, in max theres a flip uv option I'd think theres one in there if you press T, and you want flip normals tab I think, sorry not a fulltime blender user so I'm a bit rusty

[AlbertKermin]

That worked! THANK YOU!II I've been fighting with that bug on and off for days now.

[NoMrBond]

CTRL+N (make normals consistent) might also work instead of manually flipping each affected face