I might still get lucky and have the order go through.

I contacted nxPay that issued the Discover card and by an accident/bug they withdrew money from the card so that the balance was too low. I still wonder why this would come up as a faulty billing address in the Entourage system when it could have said something more useful like insufficient fund or rejected.

I still don't know if it will work before nxPay refund me the money they have withdrawn from my account and I can try again.