Recently a server that hosts some gui applications I run through ssh X forwarding from my local machine, was updated to Centos 6 and ever since then, I've had problems running some but not all applications. I know X-forwarding still works because I can run some applications like firefox without problems but for some other applications I get errors like "error couldn't find RGb glx visual or fbconfig". Interestingly when I ssh -X from a machine running Centos 6 or Fedora 15 the applications run fine without segfaulting. Also as I said, the problems only started to occur after the server running the apps was upgraded. As I don't understand X-forwarding very much I'm hoping someone here can shed some light on this. Is there a setting I need to update on my local machine? Do I need to roll back the server's Xorg?
Since only some apps are affected it sounds like the upgrade messed with direct rendering settings.
export LIBGLALWAYSINDIRECT=yes after you've connected.
You can also use -Y instead of -X to skip the X11 SECURITY extension controls that might bother you.