If you want to skip the troubleshooting/problem diagnosis and get right to the fix, go the section “Fix Action”.
Troubleshooting and Problem Diagnosis
As you are no doubt aware if you’re reading this, modding Skyrim is a crash laden journey of sorrow. Recently, I ran into one of the more annoying crashes. I added some mods and found that my game was hanging when I tried to create a new game and crashing when I tried to load an old one. I of course immediately disabled my most recently installed mods to no avail. I also attempted to fix the problem by starting entirely over by deleting all configuration in the Skyrim folder and performing a file validation check and still the problem persisted.
It was at this point I realized the problem must not be in the Skyrim folder, but somewhere else. Sure enough, Skyrim stores additional configuration in the app data directory of windows. I found deleting the Skyrim directory in appdata temporarily remedies the problem. However, after a few loads I noticed the problem returned. I browsed to the Skyrim folder in my C:\Users\username\AppData\Local\ directory and took a closer look at the plugins.txt file. I discovered at the top of mine there were two entries skyrim.esm AND Sykrim.esm. To the casual observer, they’re the same thing, but you probably noticed the difference in capitalization. Sure enough, I went to my steam Skyrim folder and a lowercase skyrim.esm was nowhere to be found. Skyrim was attempting to load a nonexistent file.
Open up a windows explorer window and type %localappdata%. This should take you to a directory similar to C:\Users\*your_username*\AppData\Local\. Browse to the Skyrim directory. Open up the plugins.txt file. Ensure all files on this list exist in your Program Files\Steam\SteamApps\common\Skyrim\Data directory. Capitalization MUST match! My particular problem was an entry skyrim.esm, which should have been Skyrim.esm.
Comment if you need help.
UPDATE: I realized that every time I install a new mod with Nexus mod manager (NMM) the problem occurs again. For some reason when NMM installs a mod it readds the bogus skyrim.esm causing the crash. I’ve just gotten in the habit of deleting it and resaving after I mod.