I have mousekeys turned on in the Universal Access menu and lots of posts as well as this documentation page:
https://help.ubuntu.com/11.10/ubuntu-help/mouse-mousekeys.html
mention that NUMLOCK or SHIFT+NUMLOCK toggles this on or off. Neither of these work for me. The only way I can apparently turn this feature off is using the Universal Access menu, which is annoying if all I want to do is toggle it off to type a few numbers.
I use mousekeys on Windows and it works fine.
I am running on Ubuntu 11.10 and my keyboard is a MS Ergonomic 4000.
I wonder if some other config setting is getting in the way?