Anyone else had this problem? I'm booking a fare BNA-MCI for this May, used some leftover funds from a ticket I'd cancelled last December, and now I have to pay for the Early Bird fee.

No matter what I do, the website comes back with "The credit card number is invalid. (SW900001)"

The credit card number is 100%, absolutely not invalid, and I want to use it because it's a PR Gold card that earns triple points on airline purchases.

What a PITA. I really don't want to call the 800 number and sit on hold forever given what people have reported about I FLY SWA this week. Anybody else dealt with this?

EDIT: Turns out I had already saved the Amex in question to my account sometime last year. Was able to get things to work by selecting that card from the pulldown menu at the top radio button. Hey, I'm happy it worked, but am still wondering why I got "invalid credit card" other than "you already saved this, dumba$$."