Sorry you were having trouble. Please try using this link http://www.panicportal.com/order_pres.html
Which credit card are you using? Clickbank (who handle the online payments) accept payments from Visa, MasterCard, American Express, Discover, Eurocard, Bravo, Diners Club, Carte Blanche, JCB and PayPal.
Please note that a debit card will not work, even it is provided by one of the credit card companies listed above. Have you spoken to your credit card provider?
If you have queried any purchase recently, or if you do not usually purchase via the internet, they may have put a hold on certain transactions. This is to protect you in case your credit was stolen or cloned or if somebody else has managed to get your credit card number.