Right, let's think. Clearly you have changed something
about your config file, else things wouldn't have changed. Perhaps you made some adjustment with the editor without realising (can quite easily happen under vi
, if you're not used to it). Let's take a look at when the file was modified:
ls -l /etc/X11/xorg.conf | cut -d' ' -f7
(change the file location if it's somewhere else in your distro).
My guess is that you've managed to mangle the ServerLayout section. This section normally refers to screens and mice, and yours doesn't, so it could conceivably throw the errors you're encountering. Adding some relevant lines in there may well fix your problem.
But wait, let's backtrack a bit. You say you backed the file up before editing it (a sensible precaution). Have you tried restoring the backup? Your posts so far suggest you haven't, and that should be the first thing to try (it's why we take backups, after all!). I'd advise you to keep your current "broken" xorg.conf in case things don't immediately start working and we have to dig around for more clues. Something like
mv /etc/X11/xorg.conf /etc/X11/xorg.conf.broken
mv /wherever/you/backed/up/xorg.conf /etc/X11/xorg.conf
should restore your backup while preserving the current file.