TL;DR version: after ~3-4 minutes (tops) spent inside Riften, on my first time visiting it, one of two things happen: either all the guards suddenly go hostile, or hordes of hostile Stormcloaks spawn in. Sometimes both. It's as if the game thinks I'm on the Imperial side of the Civil War quests and am supposed to be defending Riften or something, but...I'm not. I haven't picked a side yet.
http://youtu.be/2DnOSmIjw_E, retracing the steps I took outlined below. (And also demonstrating that I'm not on the Imperials' side and I have no bounty.) Sorry there's no sound. Either MSI Afterburner's video capture feature doesn't support it, or I need to tweak something. You can see in the video that both the Stormcloaks and Riften Guards are hostile toward me, for no reason at all.
If you'd like to try and replicate this yourself or just see it in person, http://dl.dropbox.com/u/10456033/Save%20127%20-%20Eira%20Temura%20%20Skyrim%20%2069.35.18.ess. You'll have to jog through the lake to the North Gate to get inside, first.
Full version:
My character's ~70 hours into the game. Just visited High Hrothgar. Not in any factions whatsoever. First time visiting Riften; I went in through the North Gate (after failing to persuade the guards at the other gate), paying the "entry tax" on the way in. I have Meeko and Erik the Slayer in tow. No mods, just a texture mod (for the female skin) and a controlmap mod to allow left-handed me to rebind the keys. That's it.
On entering the city, I talk to Mjoll the Lionness a bit, then get force-greeted by Maul. Persuade him into giving me some "dirt" for free. Get the "No Stone Unturned" http://www.uesp.net/wiki/Skyrim:No_Stone_Unturned from him. Move on.
I then walk forward into the city and overhear a conversation between Sapphire and Shadr. As soon as that conversation finishes (or shortly thereafter), the combat music starts and suddenly the guards all go hostile, OR a bunch of Stormcloaks spawn in. Or, as seen in the video above, both.
In short: HOLY HANNAH WTF IS THIS, BETHESDA. Someone want to explain what's going on here, please?


I've yet to have the Vigilants of Stendarr get hostile with me. Did you spawn any Daedra around them? Apparently that ticks them off. But yeah, you'd think if my killing those Thalmor was going to get the Stormcloaks after me, it would have happened when I was completely surrounded by them in Windhelm.
Unfortunately so far it's happened to me every time I go to Riften--I tested this out ~5 times in the process of recording the video. I'll try going to Riften and not starting "No Stone Unturned" tomorrow and see if that fixes it. Not sure why it would, though. Just the only thing I can think of to do differently. (Edit: I suppose the other thing to do would be try to enter the city during the day rather than at night.) Sure would be nice if I could actually go into the city without it turning into murder central, though. I've got a bounty quest to turn in. 



