I'm not exactly sure what triggered this, but I was in the Bee and Barb in Riften and encountered Sanguine. I went ahead and started the quest. I was transferred, of course, to Markarth at the Temple of Dibella. I hadn't actually walked into Markarth on my own yet, so I suspect that might have something to do with this... After I walked around and activated the beginning of "The Forsworn Conspiracy" and looted the killed lady's body, I figured I'd go ahead and take care of the Molag Bal quest as long as I was there. So I talked to the guy outside the door, went in and all the voice speech suddenly stopped. I started walking back towards the room leading down to the cavern and everything changed to that strange smoky color and things started flying, but Molag Bal wasn't saying anything. Then I walked outside and everything was still smoky and the screen was shaking and my controller was vibrating. So I walked back in, I killed the Daedra hunter guy like you're supposed to, and that seemed to fix everything. Molag Bal was talking again. I went down to get locked in the cage and everything resumed as normal. BUT when I aimed to leave the house, the front door was locked and told me I needed a key to leave. Molag Bal had locked me in! I knew those Daedric gods were no good... lol... Anyway, there you have it, another bug posted... This is post 1.4 patch, btw.

I would also like to add some things about the weapon racks floor displays... Two-handed swords have displayed (at least in the house you purchase in Markarth) upside-down (meaning the blade is pointed toward the ceiling)... I do like seeing some staffs like the Wobbajack and the Sanguine Rose displaying with the heads up. When the Staff of Magnus was displayed, it was upside-down. I mean it's nice to have the option to display anything at all, but I personally think that when I'm putting something in my house to help make my house "look nice", it should look "right" as well.

Check the body, i believe the Vigilant of Stendaar has a key...maybe.

yeah this happened to me as well, not recently i might add, i think it was patch 1.2

Reload a save from before you entered the Abandon House. That quest had been known to be glitch as hell if you enter with a follower or leave before killing the vigilant.

I don't take followers with me anywhere so that wasn't it. Voice cut out as soon as I went in. I reloaded a previous save. It glitched every time without fail. I'm just going to wait until they're done fixing all the bugs and finally come out with some DLC before I touch the game again. I would have been much happier waiting even a year or two longer for a game that works properly than having to keep going back and starting new characters just because they didn't make it without a plethora of game-breaking bugs.