If you'll read through the archives you'll see that many of us had trouble with Radeon cards .I had the same problems you are having when I was using a Radeon 6400 ,but then I switched to a geforce 5500 vid card and it hasn't crashed once ,except when I tried to experiment with modding and fouled it up .I don't know why POTC has trouble with Radeon cards ,but it does.