@AbbyFox - Did you blank out your mod list prior? The reason I ask is because this was happening to a friend of mine when we were trying to get together for a MP game. She had been running fine before, she added a mod she wanted to try, and I added it to my list as well. I could launch the game, but she crashed every time. We removed the mod from our list, yet again I could launch the game, but she kept crashing. It did not matter what she had on her mod list, she crashed, so the problem was not related to the mod themselves, but the mod launcher. She tried a number of things -- reinstalling TL2, Steam, deleting mods and downloading them again, backed up and then removed the contents of her modsave directory, tried with a copy of my modsave directory -- still crashed.
I was finally able to replicate it, and nothing I tried at first would enable me to launch the game. Argh, now I can't play at all ... However, by trial and error, I found that when in modlauncher, if I unselected ALL the mods, I could launch the game through modlauncher. Then I quit the modlauncher and manually clicked the mods to put them back on my list (loading from an .sch list did not work), and it worked. My friend did the same, and hours after we had initially tried to start our game, we could finally play. The rare times the crash has occurred since, the clear the modlaunch list and manually readding them has worked every time.