i had this problem out the blue on a 2 month old car, tried spare keys never used, still the same, then i opened door manualy then open the boot, hey presto! everything working back to normal ever since. i think the central locking went all out of sync and stopped working altogether and this appeared to reset it, had the problem when it was a deep frost, don't know weather this had somthing to do with it. Give it a try anyway.