Guys, I had the same problem. I did make a seperate thread about it but I will paste what I put into here:
Well i have just finished my conversation with the Customer Service Rep in the Account and Billing department (after a 90min holding time), and the following happened:
Told him i was having failed transactions for cartel coins and that none of my payment methods worked (visa credit, vis debit and paypal).
First of all, he looked into the payment history to see that there was a record of failed attempts, to confirm that the cards were ok i asked him to process coins through both my visa credit and visa debit cards. These went through, confirming that my cards were ok.
I then asked him what the issue was and he said:
We have noticed a trend occuring with this problem. Against the accounts we think there is a cooldown period of 24hrs after purchasing 5-6 lots of coins. If you are to purchase any more once the cooldown period has been implemented, your account is blocked due to the account automated security assuming that someone else has hacked your account details and is purchasing against your will (which is quite a nice anti-fraud device, although it is annoying getting it removed.)
It was recommended to only make up to 4 purchases per day. To remove the block you have to phone up customer services for an action to be placed on your account. This action is then dealt with by a different team.
Well i hope that this has cleared up the issues for those who have the purchasing errors.
Good luck all.
I hope this has at least put the majority of you to rest