Sam Guevenne,
who is for whatever reason standing outside of the inn, on the steps, will not move. And so now Carlotta Valentia and her daughter stand outside near her stall, 24/7. They never move, they never speak. I can still buy vegetables from her, but that's all.

Ysolda also has stopped speaking. All NPCs have stopped chatting with each other, completely.

What is going on???

I had a similar thing yesterday, i was fighting a dragon in one of the open villages, everyone in the village started to help and run for their lives ect, then everyone just forgot about the dragon and stood there, doing nothing till i restarted the game and reloaded my last save. weird..

This (or something like this) has happened to me three times now with different actors, most prominent example being Arngeir of the Greybeards (who is a quest giving actor and quite important). I found him like this, kneeling in the main hall of High Hrothgar.
I am not sure if it is the exact same problem, though. In my case, individual actors would completely freeze up, no idle animation, no idle pvssyr, not moving or following their schedule. Hovering the crosshair over them still gives the “Talk to” option but pressing E does nothing.

I have no idea what circumstances cause this.

So far I could always fix the problem by opening the console, clicking on the actor, disable and immediately enable him again. He would vanish, fade back in and return to normal behavior.

Maybe it helps you.

Won't this become a major problem in the game? Carlotta and her daughter are standing a few feet apart, staring at each other. 24/7. They don't move from this position. They still turn their head and face me when I walk by, but they make no comments (you know how NPCs make comments when you get close to them, that never fails). I remember when the game was new, that little girl would not just stand there in place all day, she would run around with that little boy and play tag. Carlotta would go into the inn and sit down for a drink, and she would go home at night. Now she stands there and never moves from that spot. She will still sell vegetables to me, but she won't move.

Ysolda also has stopped making comments to me. She still walks around...

Sam Guevenne is still standing on the steps outside the inn and won't move. I guess the only way to get rid of him is to have that drinking contest. Maybe he is the reason everything is broken.

The little boy that used to run around with Carlotta's daughter, keeps leaving Whiterun. He just walks out the gate and starts walking out to the farms. I have no idea why he's doing this. He used to stay in the city.

Jon Battle-born used to say, "Damn those Graymanes to Oblivion!" every time I walked past him... now he just walks around the city aimlessly, and doesn't speak anymore when I get close to him.

I think the game has broken on me.

I've been noting AI issues quite a bit, the most outstanding ones are bandit AI not responding to the player presence or guard precense, there's a guard post with two guards not far from Whiterun, 4 bandits were just standing in front of it, there was no reaction until I attempted dialogue, up until that point it was like the guards and my character were invisible, I've also witnessed this with draugr.

This reminds me of Morrowind. If anyone recalls, as time went on, all the NPCs in the world were slowly sliding in a particular direction. The guy standing on the silt strider platform would fall off, eventually. People inside buildings would be pushed up against the walls. And since NPCs never moved in Morrowind, this became a serious problem. But it was all relative to time, or so it seemed. And 57 days have passed in my game (and by the way, NO dungeons have respawned, ever... so the whole respawning dungeons is a freaking lie!)... the more time that goes by in my game, the more oddly the people act.

They have become self-aware!