Account needs conversion? Can't log in

I am unable to log in to my account using the Mists of Pandaria client and receive a message about needing to convert my account into a Battle.net account, the link for which leads me to a 404 error page on the battle.net site.

I've been able to log in to the same account on WotLK no problem, but on Pandaria I cannot. after closing the pop-up for account conversion, trying to log in again results in an infinite wait staring at the connecting... window.

I've tried the fix suggested in http://forum.warmane.com/showthread.php?t=352851 to no avail

I'd appreciate any help.