Ah, Civ4. A near-perfect illustration of the karmic principle that great joy has to be counterbalanced by great suffering. And with Vietcong 2, strong evidence that Take2 Interactive won’t let QA get in the way of a release date.
If you have a look through the user forums, there are good number of problems with Civ4 - many related to the graphics, which are actually quite demanding for what is basically a top-down strategy game. And it does have a number of random quirks. I installed it, but it absolutely refused to start. Many reinstalls and much research later, I came across a solution - create a separate user account for Civ4. Now, it works flawlessly, provided I log into my special Civ4 account. This is not usual behaviour for well-designed and tested software.