I just installed ut3 retail and have been having some graphics artifacts during play. Large polygons simply disappear and flicker all over the screen. I've seen a similar thing happen on my old PC and it was due to overheating, but I don't think that's what's happening here. It doesn't happen in any other games, including crysis demo, cod4, hl2, portal, and even the ut3 beta. Only ut3 retail shows the problem. I've set all my graphics settings the same as I had them in the beta (1280x1024 max everything, intense shader). It only happens on some maps. Suspense, Heatray, and Shangri-la don't seem to have a problem, which is probably why I didn't have any problems with the beta.
nVidia 8600 gts
2 gb ram
Not sure the version, but the video driver is less than a month old.