Try
this link and change the UT.ini file to look like this-
[OpenGLDrv.OpenGLRenderDevice]
UseGammaExtension=1
UseModulatedGamma=0
UseS3TC=1
UseTNT=0
MinDepthBits=32
MaxLogUOverV=8
MaxLogVOverU=8
UseMultiTexture=1
UsePalette=1
UseAlphaPalette=0
ShareLists=0
AlwaysMipmap=0
DoPrecache=1
Translucency=True
VolumetricLighting=True
ShinySurfaces=True
Coronas=False
HighDetailActors=True
DetailTextures=True
UseTrilinear=True
MaxAnisotropy=16
SupportsLazyTextures=0
Instead of the setup listed in the article(this is a newer patch, even newer then the one I linked above which is for the 4.32 version(this is for 4.36), probably should do another update). Also, as odd as it may sound, disabling VSync tends to clear up the flickering textures.