Mini-map graphics glitch

[Raisin Bran]

All the games I played there was the same mini-map graphics glitch.

The Minimap (bottom right of the screen) reacts weirdly. I can see the map fine but some zones of the map are gray, Im not talking about the fog of war. I'm saying that some gray squares appear randomly on the mini-map.
It did not happen on the Vanilla CIV.

 

[Edgecrusher]

I was actually having a similar problem. The mini-map would turn black (as if it were un-explored) Except the city locations remained visible.