I finally got through in IE by deleting browser history, cleaning out cookies, history etc and rebooting.
I can confirm though you don't have to use a Visa card, I used American Express and there was a choice for Mastercard.
Had something to do I think with the Ticketek profile, you can't go forward to pay for tickets and you can't go back to clear whatever is blocking it, you have to start again by clearing any connection to Ticketek (couldn't even create a new profile to by-pass the issue). Clearing Cookies by itself didn't seem to work either, perhaps eventually my connection timed out and that let me back in.
I tried Chrome as well and had the same problem.