Numeric keypad not working

I am running Ubuntu 10.04, fully updated, from an external USB hard drive. Everything works really well, except the keyboard. The numeric keypad is not working. The keys don't do anything, with or without NumLock on.

The Keyboard Preferences are set for Generic 105-Key (Intl) PC. The keyboard itself, on this computer, is PS2.

Any ideas where to look for trying to fix this?

Sometimes, in machines that I connect through VNC mouse keys get mysteriously enabled. Maybe this is your problem.

Click on the System Menu -> Preferences -> Keyboard. In the Mouse Keys tab check that Pointer can be controlled using the keypad is disabled.

I'll post another answer because it took me ages to figure it out. It appears that things have been moved around a bit in recent releases. The "Mouse Keys" tab wasn't there in my Keyboard preferences (Ubuntu 11.10, gnome shell), so @JavierRivera's solution set me on the right track, but didn't solve the problem of turning off the "control pointer using keypad" option. This is where I did find it:

Settings > Universal Access > Pointing and Clicking

I also enabled "Numeric keypad keys work as with Macintosh" since I'm using an imac keyboard. This option is found in:

Settings > Keyboard Layout > Layouts > Options > Miscellaneous compatibility options

which seems to be necessary for me.

For Ubuntu 12.10:

• Click on the System Menu -> System Settings -> Universal Access -> Point and Clicking

• Turn "Mouse Keys" off

If you are using XFCE4 (e.g. Xubuntu):

• 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)