The character copy service for the Mists of Pandaria is currently undergoing maintenance according to Community Manager Lylirra on the official forums. This maintenance is to address an issue affecting the service, and there's currently no ETA on when the character copies will be back up. For those who were invited in the latest round of 250,000 invites, this means while you may make a new character on the beta servers, copying your character will have to wait for a little while.
It's open warfare between Alliance and Horde in Mists of Pandaria, World of Warcraft's next expansion. Jump into five new levels with new talents and class mechanics, try the new monk class, and create a pandaren character to ally with either Horde or Alliance. Look for expansion basics in our Mists FAQ, or dig into our spring press event coverage for more details!