So it does sound like you're having a BE system. Handful of fixes for those just landed in 10.6/11.0 I'm afraid. Although I'm not sure why newer xserver will be required... guessing you're running a old (pre glamor, or out-of-tree glamor) one ? If you're worried about messing up your setup you can always grab a recent enough livecd or install Fedora rawhide/Archlinux/etc in a separate partition.