my numpad stopped working in ubuntu code example

Example: my numpad stopped working in ubuntu

In most case pressing numpadkeys+shift to reactivate your numpad will work
if not then  
Go to Settings Manager > Accessibility > Mouse. Uncheck "Use mouse emulation"; if it is already unchecked, first check it, and then uncheck it (I suppose, for whatever reason, the GUI doesn't know the the Numpad is emulating the mouse)