I had XFree86-75dpi-fonts-4.1.0-0.5.9.i386.rpm installed. I upgraded to
XFree86-75dpi-fonts-4.1.0-0.8.6.i386.rpm. It told me that it was saving
/usr/X11R6/lib/X11/fonts/75dpi/fonts.dir to fonts.dir.rpmsave, and indeed
it did, but it didn't create a new fonts.dir file!
My first guess for why this happened is because it calls mkfontdir without
a path, and mkfontdir wasn't in my path when I ran the upgrade because
/usr/X11R6/bin wasn't in my path. But I upgraded XFree86-100dpi-fonts at
the same time, and that upgrade did create a new fonts.dir file even though
it, too, calls mkfontdir without an absolute path. So I'm not sure why the
new fonts.dir file wasn't created.
I have made mkfontdir explicitly pathed now in the specfile. This should
fix it in all XFree86 packages and subpackages. Our other font packages
need to be fixed as well possibly. I believe this should fix it in
4.1.0-0.9.0 and later. When it is put in the tree if it does not fix it
for you, please reopen the bug and provide any new info you might have to
track down the problem.