I then tried my other debit and I got the same message.
So finally I went in and payed with paypal and everything was working but once I finished the payment, it charged me and sent my back to the cart with SpellForce still in there.
After I got on to my bank page, I seen that now I have 3 charges to GoG for 9.99 and a charge on paypal and still no SpellForce. :(
So... Now I am waiting for this issue to be resolved.
But I was just wondering if anyone has experienced the same problems I have :S.