We're sorry to hear that you're having difficulties with your purchase. Because payment errors could be caused by any number of steps in the payment process, they're often difficult to track down. Please see below for a list of possible solutions to a purchasing issue.
Purchases through Mojang may be international purchases for those outside of Europe. If a credit or debit card payment is not going through, you may want to contact your card company to ask about the status of the transaction.
If you received a message asking you to wait 48 hours before you try your purchase again, that is a security restriction when purchasing through Moneybookers (for credit/debit cards), and Mojang cannot lift that restriction.
Paypal is not currently an option for purchasing a Minecraft gift code online. However, you can still purchase a Minecraft account using Paypal.
Due to US law, many or all prepaid debit cards purchased in the US will not work for Minecraft purchases through Moneybookers, as the company is located outside of the US.
Sometimes a payment is unsuccessful when an unsupported payment method is used.
If you live within the state of Illinois, the Moneybookers website lists this location as "coming soon". Some users have reported success by selecting a different state during the purchasing process. Alternatively, prepaid cards are now available in US retail stores, and are coming soon to European stores.
Additionally, you may wish to try a different method of payment, or try your purchase again.
If you experience further difficulty with your purchase, you may wish to contact Paypal or Moneybookers, depending on your method of payment.
Paypal: www.paypal.com, click "contact us"