I was standing outside of the building, doing the guard thing. A few NPCs had come and gone.
An NPC named Pacer walked up and talked to the other guard for a short exchange.
Pacer was in the process of delivering a line to the guard about not wanting to go inside, he had errands to run or something. While he was delivering that line, I was farting around with my mouse and I ironsighted Pacer, and he interrupted his line to speak to me to complain about it.
The dialogue exchange between the two NPCs stopped, and the quest could not move forward. I threw evp/resetai on both NPCs for the heck of it, but, no good.