Thanks for your post on my thread.
The fact is that mods shouldn't do this. I doubt any mods you added would effect the ending. The performance dll file, I also added because frankly the framerate slowdowns were stupid, I will try removing it and get back to you but the popularity of this download highlights that the game was not ready for release, that this was a persistent problem that bethesda/obsidian failed to address.
I can say that I have the same problem, and I have not used any mods. I did download the directx performance fix, but I cannot fathom why that should affect the endings, if it IS causing the crash, then frankly, someone needs to fix this in an official capacity that makes the game stable AND able to run on machines that require this fix. I don't think it's a lot to ask the developers that they maximise the stability of machines that ran fallout 3 without a problem, especially considering I have noticed no significant graphics upgrades.
this game engine has been fraught with problems since oblivion, and yet problems from that game still exist! (anytime you pick up an object off a surface all the remaining objects decide to levitate) or the inherent difficulty with FFDShow? These workarounds have been fixed by modders and tweakers, the developers couldn't address these issues? I'm getting off my soapbox now

please let me know if you make any headway, I will likewise do so.