Giving users a clue

Now that I am all fired up about usability after UI13, I am particularly annoyed when a company can't provide a decent error message.  While purchasing a ticket on AirTran, this is the error message I received when trying to make a payment by credit card.

Does this improve my user experience or create a more positive perception of their brand?  I don't think so.  Please, test your forms and read your error messages and make sure they makes sense to the user.  Granted, I figured this one out - but why would they make the decision to display that text instead of, "Please check your credit card number, it seems invalid so you may have entered it incorrectly. If it appears correct to you and you're still having trouble, a customer service representative can be reached at etc..."