That graphics card I had went boom 3 weeks ago. So I assumed that this problem was part of the melt down on a year old PNY GeForce 9800 GTX+.
I replaced it with a GeForce 250 GTS NVidia. Unfortunately, I was flying in the scenario today, looked left and someone keyed their mic. The game hung, then when it came back 2 seconds later the sky was dark grey, the ground was white and the trees were still showing. This was on the Rhine Summer terrain, using the converted file.. just like the converted file for Ardenne Summer.
Why would this happen to two different cards and two different sets of drivers?