Every time I go to checkout I am told my card details are incorrect, but they are not. I have to re-enter the same card details from scratch each time, though they are already on your system. I don't mind if the issue is to put in a security number (which is good practice), but that is not what I am told. I am also OK with you not saving my card. However, saving it but then failing to use it without explanation -- consistently -- seems a little silly.