I'm having the same issue.
Just upgraded accounts a few hrs ago... perhaps I'll try again tomorrow and hopefully the accounts will have upgraded.

Also, this might be related, I'm dual boxing on two new accounts. Then, when these two new chars reach lvl 25, I was going to join them with my existing account. So, there is no established account to group to. Could this be the problem? I hope not, since I don't want to wait 10 days before using these new chars.

Thanks.