Lately I've been playing Oblivion with Nehrim, the total conversion mod, and it has started to crash at various times and corrupt most of my newly created games. I'm running Steam GoTY version (which should always have the latest patch) + Nehrim with latest English patch. I'm about 100 hours into the game, and until now, Nehrim was running without any issues of such sort.

I've come up with three possible reasons for this:

1. CPU overclocking - proved to not be the case, as resetting clocks to stock values does nothing to help the issue. Having OC'ed my CPU a couple of days ago, the possibility had made me worried.
2. Save game bloating - I've been playing Nehrim while exploring every corner of the world, but with 100 hours in the game, I've covered only Middlerealm (about 1/3rd of the mod's content). The latest save is 3.8MB in size.
3. Damaged/corrupted game files - I had made a backup of vanilla Oblivion before installing Nehrim, and so I tried reinstalling Nehrim over the backup files. It did not help the issue.

Just to be sure, I'm running Windows' error check tool on my game partition (came up with nothing), but I'm the most worried about the second, save game bloating possibility. Is there any fix for that? Is there something else I should take in concern, or any possible fix I should try? Any help will be appreciated.