Update 2: NVIDIA gave us a call and they told us they were trying to recreate the problem and that they were partially "successful". Basically, they can encounter everything BUT screen corruption (artifacts and other beasts) – i.e. the fan indeed stops blah blah. They also told us that their chips are tested in an oven to make sure they work without any problems at temperatures around 100C. So, their current conclusion is that our board is a black sheep... NVIDIA couldn’t get DiveVision screensaver to work "as advertised" but OpenGL Pipes and Matrix Reloaded worked fine.