My old hard drive died (earlier post), and I'm now running Win7, but my game has developed an odd habit with its graphics:
Sometimes, after leaving interior cells at night, the environment reverts to being absolutely dark, with glaring yellow exterior lighting. Sometimes it stays normal, with good ambient light, certainly enough to see with.
Last session, I actually walked past a master vampire attack in Whiterun, because I couldn't see it under the smithy awning because of the dark.
It doesn't appear to be a mod issue, as I earlier thought.
Any suggestions or ideas?