The same thing was happening to me a while back, it wasn't the bank or anything from my side. I sent in a ticket and got a response in like 2 days saying they "reset" my account and I could buy again. I suggest sending a ticket.
I had the same issue. When I contacted paypal, they said their automated internal fraud system flagged the account. You have to wait 48 hours with 0 transactions against the offended and then try again.
Thank you both!
I submitted a ticket to GMG as first measure. I'll wait for their response and try again (though I'll miss the BD deal :(). I hope I can purchase from GMG after that, I've been mising way too many deals