This solution worked for me on both operating systems. ( Lubuntu 13.04 / Xubuntu 12.04 LTS)
sudo apt-get install numlockx
sudo leafpad /etc/lightdm/lightdm.conf
add the next line at the end
I have installed lubuntu 13.04 and been trying for hours to have the numlock on after booting. The numlock is enabled in the bios, and I tried a lot off ways to get it work. 'https://help.ubuntu.com/community/NumLock' and 'https://help.ubuntu.com/community/Lubuntu/Keyboard'.
I don't see how I can make it work. Any Ideas? I'm new working with the command line so It isn't unpossible that I made some mistakes.