Hello, I'm getting an error where I can't enter the Thirsk meadhall by the main door because it has somehow been modified, and now it acts like a normal "open/close" door (leading to an empty space, as if the meadhall was hollow), instead of taking me to Thirsk' interior. When I open the console and click on the door, it shows:

"ex_S_door_double_fixed"

...but that doesn't give me a clue of which mod is causing it. Can somebody help me?

After doing that I suppose you could try an ori command

This sounds familiar, do you happen to have http://www.gamesas.com/index.php?/topic/1098203-missing-thirsk? If so, check the linked thread for a fix.

Once you find the ESP that's causing the problem, open it in the CS:

Open the door's reference window by double-clicking on it, then set the Teleport to load the correct cell. (the interior of the Hall)
The click Select Marker, wait until the cell loads, then place the Pink Arrow (the DoorMarker) in the correct place.
Save, exit.
Probably a good idea to Update your Save file with Wrye Mash too.

Thanks, that seems to be the REAL problem...I'm looking if someone could send me the patch...