Install of KB2686509 failed on one of my XP machines. (I know I was advised to hold off - but I didn't listen). The KB article on files in the wrong place did not apply. But I did have KeyTweak installed to kill the caps lock key.
What I learned. Don't uninstall KeyTweak - that won't help. Rather ask it to restore defaults. (reboot) Then apply KB2686509. (reboot) Then restore your settings and, of course reboot! (Oh do I love the update process on my Debian Linux server!)