Before you give up, take a look at this directory:
ls -l /usr/X11R6/lib/tls
and if you see files there, try moving the directory while you're playing ut2k3, and restoring it afterwards.
mv /usr/X11R6/lib/tls /usr/X11R6/lib/tls.sav
put tls back:
mv /usr/X11R6/lib/tls.sav /usr/X11R6/lib/tls
note: of course, if that actually worked, then slap those into some little shellscripts like bin/preut and bin/postut and invoke ut in a way that makes it all transparent. If it doesn't work, it was worth a shot
This may be totally unrelated to your distro, but on some, X has Mesa installed and ut2003 will look there first, instead of heading for /usr/lib/tls (or wherever they're supposed to be on your distro). Another version of this is uninstalling any Mesa libs, but that's drastic considering that some apps are happier with them there, and other's like ut* and q3* aren't.
as I reread your messages, I think the odds of this helping you are slim because glxgears doesn't even run. It shoud at least run, even if it runs poorly with either set of glx files.