It's been some time since i started UT for more than 5min, after i bought HD 4850 some weird problem appears in UT, doesn't matter which rendering i choose, i tested them all (at least all i can think of :p) and each of them gives me slight screen tearing in the middle or top of my screen. Thing is, it's normally not visible, only when i move or turn around quickly. I wanted to play some more UT but this is really annoying issue, any ideas what might cause it ?