Just a thought... doing some snooping around the installation and found this
X:\UT3demo\UTGame\Localization\INT\ReadmeDemo.rtf
[quote:3edd36f3e1]Some issues with ATI graphics cards cause the game to stop: To run Unreal Tournament 3 for Radeon 9x00 cards, we recommend installing the ATI Catalyst driver revision 7.8 from the www.amd.com website. If you do not install the revision 7.8 driver from the website, at some point the game might stop and your progress will be lost. For newer cards we recommend installing ATI Catalyst driver revision 7.9.[/quote:3edd36f3e1]