I have an existing Google market account which I have been using frequently to purchase apps. I tried to buy a new one today and I see my card listed as unusable for this purchase and it is greyed out. Just to test it, I tried several other apps with the same result. I then tried to purchase an app from a developer from whom I had bought before but with the same result. Nothing changed, my card is fine, its a visa. Does anyone else have problems purchasing from the market?