So, I modded the player home interiors, and aside from a few minor easily fixable and/or completely expected issues everything was working fine when I was running the game with just the 1.5 patch and using whatever version of the CK we were on when that game patch was current.
I finally updated the game to 1.8 and let the CK update as well, in large part because some issues (like the navmesh bug) were reportedly addressed in the later versions. Because of that I decided to mod the houses again from scratch with the new CK/game files in place. Basically I just recreated what had already been added in the previous mods that ran fine before, no big additions (and in some cases things were scaled back) and nothing new that I didn't already have working in previous games.
Started a new game after finishing all of that, bought Breezehome first, went in, everything worked fine and looked great. No problems whatsoever. Then I went to Windhelm and Blood on the Ice triggered and as soon as I tried to go into Hjerim I got a CTD as it tried to load the interior cell. Can't even COC myself into the place as that crashes the game as well. I got curious as to whether it was just Hjerim (because: Hjerim) and tried to COC myself into Honeyside, Proudspire, etc. Also got a CTD trying to load the other player house interiors but can COC into Breezehome with no problems and still enter it normally as well.
So I disabled and removed all elements of modded player homes, reloaded, made a new save without the mod, got out, went back in and loaded the last save and tried again - still CTDs when trying to load the interior of every house except Breezehome.
Got out, verified game cache just on principle, started a couple brand new games (both with and without the modded houses) and found that even on a brand new game with totally vanilla-from-the-get-go houses, I still CTD trying to enter any of them except Breezehome. So now I'm wondering if the modding was really the problem.
Checked the Windows event log and there are indeed many, many warnings coinciding with the recent game crashes - in the category "Desktop Window Manager Monitoring" and all having to do with graphics subsystem resources being overutilized and/or a degradation in Desktop Windows Manager responsiveness.
My graphics card is a 2GB Radeon HD 6950 and has been running the game with no problems on Ultra since I got it a couple months ago, with all the houses modded in similar fashion. I've made no big changes/additions to the house interiors that I can think of that would suddenly cause the game to crash just because the GPU is overloaded. And I'm not having issues with random crashes in the game at all - it's just when loading the house interiors (except Breezehome). So... I'm kinda stumped at where to go next. If something is overheating, wouldn't I be having problems in general, not just with a few very specific cells? Do I need to look for a driver update? Is it really something to do with the modded interiors that could suddenly be causing this sort of problem when it didn't before?
Any and all help is MUCH appreciated. My game has pretty much come to a standstill until I figure this out, and if I can't even load the interiors from a clean new game I don't know how I'd ever test a house mod to see if it's functional before getting 30 levels in and buying the place only to find out it CTDs on entry.