Ive just been informed by the Jag dealer (after meeting with the Jaguar USA specialist) that there is a design flaw on the tail light assembly of XKx earlier than 2001 which causes the bulb to unseat them selves - apparantly - the assembly has been redesigned in the 2002 models but cannot be retro fittede to earlier models. So - the mystery of my continually failing rear bulbs at least has an explanation - the fix 'grease' around gthe bulbs - eaves me less than happy.