This thing happens to me from time to time for some random reason. One game I will get it the next is gone. One of the main reason is the drivers... there was a driver update from nvidia that I got and all my games were in pink, invisible tanks, and crews. So I reinstall the previews driver and was back to normal, now I run with the latest drivers from them and seem to be ok just occasionally will appear.
The other reason is that my card is in SLI mode all the time, and as far as I know this game doesn't support it(correct me if I am wrong). So it appears that it will cause problem like this.
If anyone has this problem and recently updated their drivers I suggest reinstall the old ones or check if they have new ones. Other than that there is nothing we can do from our side until relic optimizes the game.
Hope this helps
GLHF