I spoke to Aaron Thiery at the end of "Save Matthew Habashy and Atlas from Arachnos!" and I chose to kill him. Immediately after choosing that option and his figure falling to the ground, I believe I misclicked, clicking on Aaron Thiery again, in which the dialogue box from the beginning of our conversation turned up. I was able to go through a couple of his prompts, continuing the conversation. I went to the bug report forum, and when I got back his body had gone. I clicked on the prompt still on the screen and it exited out of it, ending the conversation and the bug.
Would have been interesting to see what would have happened if the body were still there and I got to the "Kill him/Let him go" prompt again, and what that would do.