This worked for me. I noticed that some people discussing this issue in various forums had multiple people in their household trying to sign up, and that was the case here. My boyfriend was able to pay this morning, but neither me or our daughter were able to do so.

So I figured they're suspending purchases from multiple accounts on the same IP address for the purpose of blocking goldfarmers and spammers. So I turned wireless off on my phone and paid for it that way, to great success.

My daughter is having less success trying the same strategy from her phone, but I suspect she tried too many times on her computer and maybe they lock it out on the account level after too many tries, as they warn you in the error message.

I hope this helps!