I'm a pandaren class monk and I found out that I can't pick the mission http://www.db.pandawow.me?quest=29678. It's a part of the main Pandaren's quests. The NPC is there, and the quest appear to be available, but I can't take it. I have a friend who can't take it also. We tried deleting the cache's folder but still we can't take that.
I found it on the Realm x10 today, 1st August 2014.
I hope you'll fix it soon.
PD: If someone did that mission on the x10 Realm, post here and let me know how did you take the mission. My thanks to everybody.