It is interesting that you bring this up. I was just having trouble with my own booking this week and it involved the Secure Code from MasterCard.

Did it even get to the point where you had the opportunity to enter your Secure Code or did you get an error before that?

If you got it before, the thing that fixed it for me was calling in to my card provider and telling them to remove my old password (I ended up needing an override because the Secure Code website STILL would not allow me to re-register). I then went on the Secure Code website and re-registered. After that, it worked on the first try.

My mother's VISA was blocked as well. However, hers was due to the fact that the credit card company suspected fraud and nothing else. Calling in and asking if they had blocked a transaction may help too.

Hope it helps.