I have this problem too i ma running it with a 8500 512 mb ram card and sometmes the coulds looks ok. but I could not set a heavy avercast because i got a CTD with a error message This happens if i set finnes to 10.
Also there is some times that it works !!!
So i reinstall the game compled (FC 1.12b) and the problems still there i think is a problem with drivers or the game runnig with a 8XXX series of Nvidia cards.
i have make a treak on the lockon page
http://forums.eagle.ru/showthread.php?p=589661#post589661 And i have make references to this post on that forum lets see if there is a solution.