I made the mistake of upgrading my Powerbook to Fedora 10 yesterday. As I was about to do some Jato hacking today, I noticed that the up arrow key caused Gnome to attempt to take a screenshot. So I googled around, found nothing useful, eventually fiddled around with Xorg config and, of course, hosed X.
I then started messing around with /etc/sysconfig/keyboard (not knowing what I was doing) and hosed my keyboard completely. I eventually figured out how to boot to /bin/sh from yaboot (regular init had the wrong keyboard configuration) and was able to restore console access, fix my Xorg config, and now I'm back to Gnome. (I "only" spent an hour on this.)
Of course, the up arrow key still doesn't work but at least Gnome doesn't attempt to capture the screen now.
Update: Apparently I had changed Xmodmap in Fedora 8 and after reinstalling some xorg components, I have my keyboard in somewhat working state. I'm still missing curly braces so no hacking on this laptop...
Update 2: I ended up adding this small .xmodmap file to my home directory:
add mod5 = Super_L
which effectively makes the Apple/Command key function like Alt-Gr on PC and now I have a fully working keyboard! Yay!