I managed to get pass the general error the Store gave me, so here's what I did:
Note, I only did this with a Paypal account and not sure if it works for credit cards aswel.
1. Go to your account
2. Then go to Subscription
3. Click "Show your payment history".
4. Delete the saved Paypal account by clicking the cross. And then obviously click "Yes - Delete Saved Account".
5. Now go back to the Store
6. Click the item you wish to purchase
With me at least it did not skip two steps and give the error, but let me chose the payment method manually.
Had no problem paying my Cartel Coins and the Pre-Order expansion after this.
Hope this helps some of you guys!
I am not an tech expert, but it would seem to be an issue with the webpage, thus not an issue with Paypal or any banks.