Have you got a spare card you could try in the slot ? If this works it narrows the problem down a bit.
It could be either a card reader or the keycard at fault IIRC.
It could just be fluff in the card reader slot. May be worth trying to put a narrow nozzle of a vacuum to the slot and get out any cra4p thats in there and see if that does the trick.
Currently in dave_mezza2006's garage:
2002 Ford Mondeo 2.0 16v LX. Used to own a 2002 Renault Laguna Privilege 2.0 IDE & a 1998 Laguna 2.0 8v RT Sport