I’ve had this annoying thing about my keyboard layout being US for my login window in Kubuntu 12.10. This happened after I got a new wireless keyboard with this unifying usb thing at work. I recently upgraded to 13.04 and the error followed, so I dug up the workaround / fix at bugs.launchpad.net .
My fix was adding this to /etc/lightdm/lightdm.conf
[...] display-setup-script=setxkbmap no [...]