This version of the Gamebryo engine seems to have a LOT of trouble handling advanced graphics and sudden changes in frame rates. I seem to recall Oblivion doing this a bit, too.

I say this because I enabled high quality lighting in Fallout.ini, which bumps up lighting throughout the game with a small performance hit. One side effect seems to be frequent crashes to the desktop whenever frame rates radically change. For example, when moving between interior and exterior cells, or when accessing the Pip-Boy, frame rates can shoot up into the triple digits, if only briefly. Crashes seem to happen at that precise moment, and can be a real hassle if frequent saves aren't made as a safeguard.

I have installed the Unofficial Fallout 3 Patch, which I suppose is par for the course, right?

Reguarding those crashes, have you had them and do you know how to resolve them, other than setting the extra high quality lighting value back to zero?