Just played for about two hours straight with all mods enabled, except one that I wasn't sure I wanted anyway - and removing it hadn't solved the problem before so I don't think that was the culprit. But I've gone from Whiterun to Solitude (on foot) with quite a lot happening on the way and NO CRASHES.
I swear I don't know what else to think, except that all the other stuff I looked at was a series of false leads and suspicions and it all just had something to do with Steam crapping out constantly for some reason. Altho why that would lead to a system crash and not just the game crashing to desktop, I don't know.
I'm completely stumped, but as long as things are running fine I guess I won't worry about it until if and when the problem repeats or something else goes wrong.
