I'm working on confirming this problem. In the meantime, I googled the error code you got and found a thread on the Nintendo tech support sites. This code has been coming up for people since June last year, even in the states, and is often related to high volumes of traffic. I'll quote one user;
"IF you are going to a screen asking if you would like to add $20 to your account, your card IS valid. There are traffic issues at the moment, Nintendo has confirmed this.
If you do not see the $20, your card is invalid, if you do not believe this, try to change one digit on your card, you will not see the $20 screen."
Essentially, if you start seeing the next screen mentioning the money amount before you get the error code then it's a server error and it will work. If the code happens before anything loads at all, the card won't work. Keep trying the cards, and please let us know what's happening in the meantime. We would love more details as well, at which step the error happened, etc.