Well, it is known in many cases when an online game launches it will be fraught with bugs and errors for the first hours, even days. It has happened once more with the launch of the second wing of Curse of Naxxramas.
Reports are coming in from all over the world of an error which prevents players from unlocking the newly released wing. Some were lucky enough to unlock it without problems (Trump, for instance who did a nice run of the Normal bosses + class challenges)
In the meantime, for many players from all 3 server regions (Europe, the American and Asia) this was the sight that greeted them:
A few minutes before writing this post, they had closed the store altogether.
We can only hope that this issue will be solved so that all will be able to enjoy the Plague Quarter, whose review should be up on this site sometime later today.
P.S. Give your impressions about the previous wing in the comments. Recounts of any fun exploits will be appreciated.