Okay, I have no idea what the heck is going on. My newest character is working on building a house with Hearthfire and so he's raiding some mines. I started him at Dawnstar and had no problems with the two mines there. Later I went to the Rockwallow Mine (near Morthal) and when I went in, it was pitch black. My UI worked and I could interact with iron veins and the exit, but I couldn't see a thing. My character was invisible and a light spell didn't help at all. It's like none of the graphics loaded. After getting frustrated with this, I quested my merry way along and today I wander over to the Whistling Mine south of Winterhold. Same problem. I've only had this at these two places and haven't really checked anywhere else. Anyone have any idea what the heck happened? If you need more info, I'll be happy to provide it. I checked my mods and I only have one that affects mining, and turning it off didn't change anything. I've not had this happen before I installed Hearthfire and Dragonborn, but there was a long lapse in gameplay so I don't remember hitting any issues like it.
Any help would be greatly appreciated.

Edit: To add to the weirdness, the autosave the game creates when I enter the mine shows a screenshot with everything working correctly. ...I got nuthin'.