I was getting this same error, customer service didn't help. I was told to "reset my cashews and cookies" and wait a few hours or until tomorrow due to demand, or create a new account and start over.
It finally worked! At the bottom of the page, there is a "Manage Cookies" link. I clicked that and accepted and my payment went through. I did end up waiting a few hours since my last attempt, but maybe that did the trick?
