UT GOTYE and all Unreal 1 engine based games are grossly incompatible with processors that use technology like SpeedStep to adjust CPU speed depending on load. They also have issues with multi-core processors.
Once the FPS goes over 300, the game either runs too fast, or runs too slow.
A fix I have found that works is here. This is a modified game launcher for the games which is provided at the bottom. It uses a little bit of code voodoo to make the games based on the Unreal 1 engine play nice with SpeedStep CPUs and multi-core CPUs.
http://coding.hanfling.de/launch/
It should be pretty easy to install and setup. However, I never tested it online so I don't know if anti-cheat modifications are going to boot you for it.
Give it a try and see what's what. You can always just uninstall it.
I use the Deus Ex launcher and it works perfectly, but I've also tried the UT one with success as well.
Edit: I forgot to mention, this is a Windows only fix. There is however no reason it shouldn't work with WINE, Crossover, virtualization applications, modified Mac Cider launcher and such.