Tried to zone into e.star cavern and got this.
Turns out if you type /quit at the loading screen, the yes/no kills the loading screen and shows the UI again. That in turn permits you to read chat and otherwise interact with the UI .. and to see just what is causing the loading screen hang itself.(Dungeon Master): This small cavern near Eveningstar conceals an entrance to the depths of the Underdark. Once held by the Drow, the cave is now guarded by the Purple Dragon Knights.
(Error): Recovering from failed teleport...
I've never noticed the message from an actual failed scroll/spell teleport, but I'm wondering if that isn't exactly the same thing going on here (ie. failure by design, applied a bit broader than intended) .. yet it doesn't punt you into the sky above market, perhaps because it's not a scroll/spell teleport.
Anyway, once you see the "failed teleport..." bit after trying to zone, it won't ever come back. It's permanently hung -- time to kill the client.