If the IG3 demo is crashing immediately then the problem is due to your refresh rate being set above 60hz. At first I couldn't get the demo to work at all and it would crash immediately because I was using RivaTuner to fix the refresh rate problem with WindowsXP. Setting it back to 60hz fixed it though. I'm sure this will be fixed for IG3's final release so we don't have to play at a nasty refresh rate.
BTW, the demo I played was the Matrox one, a new demo is said to be out sometime in december and will feature a new user interface among other things.