I just tried to purchase some zen using an Ultimate Game Card. I was able to redeem the code without any problems, but i am stuck on the "processing" page ever since (at least 10 minutes, probably more).
My current balance (near the top of the page) shows the 2300 zen, however the main window says "Thank you for your purchase. Please wait while your transaction is being processed" and the page keeps reloading every 2 seconds.
Seems to have resolved itself.
I opened another tab in my browser to see if I could transfer the Zen to STO, and the purchase history shows that the transaction was completed.
So it was just the billing/progress page that somehow got stuck. Opening the wallet in a second tab also seems to have stopped the constant reloading.