The latest patch for Civ V has an unfortunate bug. When you start the games, all mods are reloaded, and all check marks for enabled mods are clear. Even if you recheck the mods, saved games crash because they do not recognize them as the same.
This has been reported by many on the Civ Fanatics site. The publishers have acknowledged the problem and have begun work on it.
Grrrrr......thanks for the update, amigo.
Thanks for the heads-up. I'm glad I've had Steam set to offline mod since before the patch. I will keep it that way until after that nasty bug is fixed.