This happened to me some months ago while running Fedora 9 on a desktop with a PS/2 keyboard using a PS/2-to-USB adapter. Number pad worked fine since installing F9 last year. All of a sudden my number pad quit working. I don't do a lot of updates on this machine and with so many other distractions, I chalked it up to a malfunctioning keyboard and just started using the other numbers on they keyboard.
Today my keyboard starting resetting on me (number pad and other lights coming on and going off), and the number pad still wasn't working, so I figured I search for a fix.
I swapped to an identical keyboard from another machine, and got the same behavior with the number pad not working. I found this thread and then verified that my mouse was being controlled by number pad. Connecting the replacement keyboard using the default PS/2 adapter didn't change the result.
I pulled up System...Preferences...Hardware...Keyboard, and on the "Mouse Keys" tab, I saw that "Allow to control the pointer using the keyboard" was checked. I have no recollection of selecting this, so I thought that it might have been set after a yum update.
I searched a little more and found this thread: http://forums.fedoraforum.org/showthread.php?t=188820
Apparently, typing "CTRL-SHIFT-NUMLOCK" toggles this setting.! My guess is that I inadvertently hit that combination of keys at some point and caused the number pad to quit functioning as a number pad.
Keyboard is much more fun to use now.