Uh yeah, I've been having this as well. I'm on PS3, though. I don't get the actual error notification, but the login/password box fails to load, and I need to reopen the client multiple times for it to appear. I also occasionally click play and nothing happens, but usually it allows me to access the game.

This started happening right after my game froze during an instance 2 days ago. Not sure if it's related or coincidence.