I imagine you're running Gnome (The default), which I don't use, but it sounds like you've enabled "Mouse Keyboard Emulation"
On my KDE system, it's toggle-able with ALT+F12, I'll check here in moment for Gnome.
(Gnome users: How to get numpad out of "mouse emulation" mode. Try SHIFT+NUMLOCK (Setting may be found in Universal Access) )
Some Pictures... 'cause pictures are cool! (My sincerest apologies to the Gnome users, as I don't have a Gnome machine to take screenshots)
The two modules in System Settings to look at for mouse emulation settings and information: "Shortcuts and Gestures" and "Input Devices".
I've circled the important things to select, "Global Keyboard Shortcuts", "KDE Component: KWin" and the hotkey in question: "Mouse Emulation: ALT-F12"
And in the "Input Devices" Module: Choose the mouse device, then examine the checkbox for "Move pointer with keyboard"
Hope this helps.