Thanks to this post, I’ve managed to fix a rather severe display problem under Fedora Core 4 by downgrading X Windows to the version included with FC itself. The steps:

rpm -qa | grep xorg > download.txt
pull the correct file names off the FC4 CDs with the lower versions, then:
rpm -Uvh *.rpm --oldpackage

Fairly straightforward – the hardest part was finding the proper files, which actually consisted of just going through all four CDs and doing cp ∗xorg∗ /root/fix, then running the above RPM upgrade command from that directory after weeding out the RPM files not listed in download.txt.