Is there any way to create a log of all boot-up messages?

[Markus]

First have a look in /etc/X11 if you have a backup of XF86Config-4 which could be named XF86Config-4~. Just look at the dates, if you find if do:
mv /etc/X11/XF86Config-4 /etc/X11/XF86Config-4_TEST
mv /etc/X11/XF86Config-4~ /etc/X11/XF86Config-4

Another solution would be to boot Knoppix CD with the right screen etc.. cheatcodes and copy over the file to your hd-install with:
mv /mnt/hd??/etc/X11/XF86Config-4 /mnt/hd??/etc/X11/XF86Config-4_TEST
mv /etc/X11/XF86Config-4 /mnt/hd??/etc/X11/XF86Config-4
?? means your hd installs device/partition.

To exit emacs: Ctrl-x Ctrl-c http://rgrjr.dyndns.org/emacs/emacs_cheat.html
Another editor would be vi but it's not that much easier, you could also use mc or do apt-get install nano