unable to buy videos

Yesterday i failed to buy a video from chesscube http://www.chesscube.com/shop/products/videos/page/1
I was going to buy it via cubits and I have more than enough cubits for a purchase. But the button PROCEED http://www.chesscube.com/shop/basket?ba ... 2Fpage%2F1 is unclickable.

I thought that this is just a temporary bug, but as far as I see, today nothing changes. Please give back the possibility to buy videos!!!!

Hey moderators, are you going to do something or at least may be you will suggest me something?
Of course, I understand that actually noone cares till I am not buying it with real money, but at least you may tell something like "ok, we will look at the problem and find out what causes it"