I was doing the Warrior training quest for humans, talking to Harry Burlguard in Stormwind, when the dialogue with Complete Quest/Cancel came up, I clicked complete quest, but saw no response, so I then tried clicking close. After the lag caught up the quest was completed (I got xp), but I did not get the follow up, and I cannot speak with the quest giver again. Relogging did not fix the issue.
I’m now stuck without defensive stance and have to give up on the character most likely.