On the first puzzle of the quest Under Saarthal (the one with the six pillars), I enter the correct combination, but the door still doesn't open, and arrows are still shot at me. I've reloaded the game a couple hundred times, I've left the room, and it still doesn't work. What do I do?
Double-check the pillars after you have set them all and before you pull the lever -- there is an extra little "trick" there that will become apparent after you set the last pillar and then check their state before pulling that lever.
Specifically, turning some of the pillars will also rotate others, and you have to set the pillars not only to the correct combination, but in the correct order to avoid undoing your work. I don't recall the exact steps, but I set the combination going clockwise around the room (starting with the first pillar on the left), then re-set the pillars (again going clockwise, more-or-less, I think) that were no longer in the correct position.
I spent an hour on this one myself, and only realized what was happening after putting the game away and coming back to it the next day. Once I realized what was going on, I got through the door pretty quickly through simple trial-and-error.