Are you sure the keyboard is plugged into the correct socket? The keyboard socket is usually coloured purple, the mouse is green.
If this is ok then you either have a faulty keyboard or a faulty controller on the motherboard, to test this try another keyboard or try your keyboard on another system. If it proves to be the controller you may have to go to a USB keyboard which may be ok depending where the problem is All things are possible except skiing through a revolving door.