I have a slightly fast machine and the demo for Prey works fairly well most of the time, but when I get into an area with lots of curves or molded forms (caves, tunnels) I get lots of green flickering junk everywhere that slowly increases the longer I stay. Once back in a strickly dimensional room, the flickering goes away. With the 6600gt card I have the Active Profile (under Performance Settings) set on Quake 4. Anything more I can do?