Ok, I fixed it. I used Ctl-Alt-F3 to get to a terminal, logged in as root, and did
cp /etc/X11/xorg.conf /etc/X11/xorg.confOLD
Then I edited /etc/inittab , changing the default run level from 5 to 3, the rebooted. This gave me a command line only system.
Then I logged in as root, and ran "sax2". Sax writes over your xorg.conf file, which is why I made a copy with cp. I guessed at most of the items sax asks about, and when it was done I used "startx" to test it. The fonts were good now, but alot of other stuff was not good (resolution, screen shape, no nvidia driver).
I had noticed that there was a file in /etc/X11 called xorg.conf.backup, so I did
cp /etc/X11/xorg.conf /etc/X11/xorg.confFromSax2
just to save a copy, and then did
cp /etc/X11/xorg.conf.backup /etc/X11/xorg.conf
to replace xorg.conf with the backup. I then ran "startx" and the fonts looked good. I went back to /etc/inittab and changed from run level 3 to 5, and rebooted.
Everything came back good. Somehow I have lost some of the configuration I had done in KDE, but the fix was just redoing it with the KDE tools.
So why or how did xorg.conf get borked? Any ideas?