i recently bought Unreal Tournament 2004, and it played fine for the fist couple times i played it, then it started playing real laggy during single player mode. i pass all the necessary system requirements:
Required / Me
RAM: 128mb / 512mb
Processor: 1.0ghz / 2.0ghz
Video: Geforce 2 / Radeon 9600 XT
the real problems seem to be when i try and turn my mouse and strafe when there are a lot of characters on the screen. i exit most applications when i play, so i don't think its a RAM related issue. i play with all the video options on the highest, which i'm sure my card can support, but even on low, it happens.