Somehow, somewhere along the line my number pad stopped working as a number pad and instead started controlling the mouse cursor (in Windows it is referred to as mousekeys).
I use my number pad on a very regular basis and soon became extremely frustrated at this.
Here’s the solution:
System – Preferences – Assistive Technologies
Keyboard Accessibility
Mouse Keys
Clear the checkbox [ ] Pointer can be controlled using the keypad
No need to reboot, it is instantaneous and sticky across reboots.

You just fixed my problem… My numpad just locked and it was really annoying since I’m typping code.
thx
Mozilla/5.0 (X11; Linux i686 on x86_64; rv:2.0) Gecko/20100101 Firefox/4.0
Thank you very much sir.
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.16) Gecko/20110323 Ubuntu/10.10 (maverick) Firefox/3.6.16
thanks man, this was helpful!
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.60 Safari/534.30
Muchas gracias, I’m not sure how I might have accidentally turned the feature on but with my arrow keys broken it was hard to navigate without the numpad.
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.10) Gecko/20100922 Ubuntu/10.10 (maverick) Firefox/3.6.10
Thank you! Thought my keyboard was possessed, or rather about to junk it when changing batteries didn’t help.
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.79 Safari/535.11
Nice default settings strike back again.
“It’s just the default setting, who cares?”
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:14.0) Gecko/20100101 Firefox/14.0.1
Just a heads-up, in Ubuntu 12.04 (Unity) this “feature” can be enabled and disabled using the Universal Access dialogue under the Pointing and Clicking tab.
Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:14.0) Gecko/20100101 Firefox/14.0.1
Ha-ha, I found reason :D
It`s just Shft+NumLock. Turns off the same
Mozilla/5.0 (X11; U; Linux i686; en-US) AppleWebKit/534.13 (KHTML, like Gecko) Chrome/9.0.597.94 Safari/534.13