So yeah, I'm currently stuck on the 'Retrieving Character List' dialog box while trying to get into Nagrand. I'm able to log into other servers without an issue.
Thanks for the reports everyone. We are aware of the issue and our Realm Technicians are working to resolve it as quickly as possible. Please feel free to join us in the following thread where we will be posting any updates: (http://forums.worldofwarcraft.com/thread.html?topicId=27026478324&sid=1).