I have used shop4gaming for all my extra keys, and have recommended it to others to use also.

At first I had the same trouble with paypal, I asked the support from the site, and they told me to use moneybookers.

Steps to take to make a successful buy:
  • create account at shop4gaming
  • create account at moneybookers
  • order the key at shop4gaming
  • use moneybookers for payment @ shop4gaming
  • after redirect to moneybookers choose creditcard payment (that is what I did, don't know if paypal will work)
  • make the payment (there is a chance they want you to validate your creditcard, this is done by a code (SMS) send to your mobile phone)
  • complete, wait for the email from shop4gaming
I have invited myself to the game, that way I got a month free, and I had a month free on the new key. So two months == 26 euro. The new game costed me 23 euro (dollars are cheap). So I had 3 euro profit if I play the two months.