I have a strange green world map when I load a saved file after starting.
The world is green, not an even green, but a mottled green.. There are no country boundaries. You can just see all the other feature, e.g. city lights where it is dark.
If I reload an earlier saved game, same problem.
But I have found a workaround. I just restart the game completely (not from a saved game) and the world map is OK. Then I restart again and load the game I wanted in the first place, and all is OK.
2.5 dev, IA-32, version of 25 Sept.