Hey man I think I got the solution.
First: I assume you already did the whole setini "ugridstoload:general" 5 blah blah.... that fucks s*** up.
If you can load a previous save before the current save that got messed up, then this is what you do:
Open a working save game - open the console
alt tab and open your skyrim.ini in your mygames/skyrim
change to these settings:
uExterior Cell Buffer=36
go back in to your game and in the console type: refini
This should revert you back to uGridsToLoad of 5
A side note... I would not wish uGridsToLoad on my worst of enemies. Avoid this monstrosity! (although it does make the game look nice, but I prefer actually playing instead of trying to fix this s***!)
Another side note... could this work in reverse? To make uGridsToLoad values higher? I'm curious, but I refuse to try myself
Yessir, this is INDEED the solution!
I had the same issue as the OP (minus the mysterious appearance of an edited ini file in my Data folder .. or anywhere else on my box). I had the reddish models and CTD on ALL savegames. I even restored all of my game-related files from backup with no luck at all getting rid of the insideous effects of 'setini "ugridstoload:general" 5' yada, yada. I would up reinstalling Steam and Skyrim to get back to a normal game intit. Then I applied your trick on my last save in vanilla base (had to alt tab a couple of times before my game came back into proper focus to allow console commands), and voila! I had a vanilla save of my most recent game with uGridsToLoad set to 5 in my ini. I reloaded that save to confirm and then attempted to load my modded last save (original) and it crashed just as expected.
Thanks for the post dude, you saved me a couple of hours of repeat play time (NM the hours it took me to reconfig everything!).