All i can see in the map is one light diagonal from upper left to lower down and some icons - the rest is a big black void :). And it seems like i am on the orbit of the planet... very very high.
I am using nvidia 8800 GTS (the old core) 640MB.
Anyone know how to resolve this ?

I am on your situation (with 8800GT), but it happens only in a few missions. Anyway, for me at least, isnt a big problem.

Are you sure you are not just seeing the "fog of war" that the game places over the unexplored areas of the map? Other than where you are currently standing and any place you have already been, the entire map should be black.

No. On any map, at any point in the mission the map is the same: a big black screen with only a diagonal lighted. It is "fog of war", but is not represented correctly. Doesn't matter where i am or how much of the map i discovered... (though the icons are moving into the black fog)

For Aitgud: you're right, it isn't a very big problem, but the map is somehow useful in the "RTS" maps (just a little).

In my case, it doesnt happen in the rts missions.

I have the retail version of this game, but I thought it would be worth $6 to have a DRM-free version. I can verify that the map does not work in the GoG version, while it works just fine in the retail version. I've attached two images to show the problem.

I have the exact same problem. It would be really nice if GOG could fix this bug.

Same problem here

I had this problem, but installing GiantHook, which you can find under the stickied Mod thread, fixed it. I'm going to guess that it was a problem with Giants DX7 engine, which GiantHook upgrades to DX8.

I have the same problem. Yet I have an ATI HD 3850. So clearly it's not a driver issue.