I think I have found a new, or at least unpopularized, cause of instability and crashing in Fallout 3. It is my suspicion that, if one habitually uses items with attached scripts in the Rock-it launcher, then that save will gradually become more unstable. This usually is not a problem, as few miscellaneous items are scripted, but, if one uses a mod that adds a script to a common item, such as how http://www.fallout3nexus.com/downloads/file.php?id=4318 adds a script to every junk book, it can become a problem.

Unfortunately, it seems to be a gradual problem, and is thus not easy to test. On my current Rock-It Launcher using character, however, it got to the point that loading any book into the Rock-It Launcher would cause the game to CTD the next time I tried to save. General miscellaneous items did not cause the game to crash, and removing the book mod, and thus the scripts, stopped the crashes.