In my single-player game, I've just encountered what is almost certainly a bug, and one which I believe is currently preventing me from finishing Act I.
At some point during my raid on the Selune temple, my main character became unable to initiate conversation with NPCs: my best guess is that it occurred after my battle with Dror Ragzlin, and may have been triggered by the manner in which I started the fight (namely, by placing powder barrels on either side of him and shooting one with a flaming arrow) After the ensuing battle, all of the local goblins became hostile and I could no longer speak to the cleric of Maglubiyet nearby.
More importantly, however, my main character can no longer fast travel: My other characters can initiate fast travel, but my MC is then ungrouped and left behind. This has become progress-blocking for me (I think) because it is also preventing me from travelling to camp/long resting. Pressing the camp button with my main character selected yields an error message to the effect of "You cannot fast travel under these conditions", and pressing the camp button with another character selected generates another message to the effect of "One of your players cannot fast travel."
My current headcannon is that my main character is trapped in a "You like to swing that sword, eh?" dialogue with Dror Ragzlin that never fully initiated because he exploded, and now can't fast travel because she's "talking to someone".