Ran into a problem with my Fallout 3 saving, oddly enough for the first time ever. Every time I tried saving my savegame, the game crashed with an access violation. As long as I did not save, there was no problem, but hey, what's the use about not saving your game...
The problem started appearing right after I started the Broken Steel quest line, but even outside the quest line, I have this problem.

As a member of Fallout Nexus, I was nosing around the mod repository when I stumbled upon an unusual post: Crash To Desktop Begone. It explained a plausible reason for the problem: upon saving a game, a conflict occurs with the animation sequences and saving, causing the crash. Considering how well Bethesda Softworks debugs their games (see Oblivion and Morrowind), these kinds of problems are to be expected (and if you ask me, it's silly why Bethesda doesn't fix such a critical bug; then again, it might be a conflict with some mod).

Anyway, the post described a solution to the problem: blowing yourself up. Let me say that this is not a "conventional" solution (and that's putting it very softly), but as I wasn't looking forward to restarting my game all over again, I tried it out. And guess what? It worked like a charm. After blowing myself up (dropping a bunch of plasma mines, standing on them, then shooting them is a quick way to do it), I could save again, at least until the next time I ran aground.

One of the comments also stated that loading a savegame, then immediately reloading it also was a solution. And I have to agree: rather than blowing yourself up, it's more to reload the save twice, and to avoid future errors, save then reload that save will keep you going.

Both are working solutions (sort of), which have to suffice for now, at least until Bethesda deems fit to fix the problem.