If I had to speculate, I would say that Skaven / Wood Elves would be the easiest combo right off the bat.
Wood Elves would be quick and easy to model, and the Skaven, if I recall, had been completed by the earlier group that tried doing WAR before…
I had a similar problem a few months ago, and initially thought it was an overheat as well. What it actually turned out to be was an interaction with the video card and the motherboard. It appears to have been a known error with certain quad core …