All but two of the card problems (now including some MasterCards) are from Belgium and the Netherlands. We suspect it is a regional bank issue. Most of the cards exhibiting the unexplained "decline" error have been successfully charged weeks later. We're making the following recommendations: if you're having trouble paying, try again later. Or, try one of our other payment methods: Google Checkout or PayPal.
If you have any questions, please contact us.