Sorry for the delay getting back to you, been asleep gotta work night audit tonight!
Well without more information I think this might be your problem, by default UT uses SDLGL and you need to be using OpenGL so this is what you do......
Edit the following lines in either
To use the OpenGL renderer:
Hopefully that will be your fix, if not you need to copy and paste your X configuration onto here so we can make sure you got the GLX module loaded and a few other nitbits....