Yeah we had that yesterday. I took the quest, rode around Dalaran looking for mustard herbs, and got disconnected... 20 tries later (over a period of 5 hours) I still couldn't log that character in, all my other characters were fine, but Dalaran seemed to crash me out (I'm thinking too much heat on my poor connection).
Hopefully I get to do it today, or at least log in long enough to fly the Hell away from there. I missed out on last night's jewel crafting daily as well, so I am NOT a happy panda. I did play on another character, but right now the one I wanted to play was unavailable.