Okay, this is weird. FNV was working fine yesterday afternoon. Yesterday evening, after work, I decide to get rid of my ENB. So I remove it and all associated files, and re-tweak my ini back to normal (basically just turning Fullscreen back on, and re-enabling normal AA and AS).

When I went to load, I got a black screen, but I could hear the standard opening music playing. So I wait a couple minutes, but nothing happens. I fiddle with the controls, and I can hear the sound of my mouse running over menu options I can't see. So I ALT+F4 it, run FNVEdit, and no errors. So I try again. Same problem.

Since the only thing I changed was my ENB, I re-installed, and re-edited my .INI files, being sure to follow the instructions exactly.

Same problem, only now I get the ENB overlay. WTF? What did I break?

Hmm. Well I know that with TES: 4 Oblivion, this problem can happen sometimes if you have HDR turned ON, and are in some sort of interior (especially one changed around by mods a bit), but I don't know if Fallout NV has the choice to switch HDR on or off.

The solution in TES4 is to turn HDR off, but turn Bloom (or no lighting effect) on. Don't know if this will help with FO NV though. And what you are describing happens during the initial menu, not during the game itself.

Yeah, that isn't the issue.

I "fixed" it, but only by verifying file cache integrity. It reacquired a few files, and suddenly everything works again. *headscratch* Wish I knew what I did to not do it again.