OK, it’s not really broken, but I have had a problem on my Slackware 12 Linux machine where the keypad suddenly stops working. The only way I have been able to fix this, until now, is to restart KDE.
This happened to me today, so I did some research.
KDE provides a handy mouse emulation mode where, by pressing SHIFT+NUMLOCK or SHIFT+CTL+NUMLOCK you can use the keypad to move the mouse cursor. I have been accidentally hitting this key combination. Of course, when I just type on the numbers with normal work activity, I don’t notice the mouse moving.
To correct my keypad activity, I just had to press SHIFT+NUMLOCK again.