I got this game on 2/2/09. My disc broke a week later and I got a new one from store.
Today I reinstalled my game because of numerous gigs of unused mod material, accidentally deleted music folder etc..
I hadn't opened my new box before because I hadn't reinstalled. Hadn't had the need to as the game runs without CD.

I uninstalled and installed the game again (for some reason there was no option of reinstalling). I try to patch to 1.7. The patch is installed properly. Game starts. The slides go super fast and I got the ever-annoying "Fallout 3 has encountered problems and has to be closed. Send or don't send error report".
I uninstalled and installed the game for second time. Now I don't patch. Same problem.
I reboot my PC in case my computer was exhausted by the reinstalling. But no, I still get the problem.
I looked around and noticed that the CD hadn't installed Fallout.esm. Confused, I reinstall for third time.
Now Fallout.esm appears in Data folder. I'm happy by this turn of events and start the game via FOMM.
But no. The slides seem working properly now but I still get the error report by the BoS paladin screen.

This can't be hardware-caused. Because I had ran this game perfectly for past 7 months and all problems on the way were caused by mods and DLCs.


Theories:
1) As the .ini files were apparently not removed and reinstalled by the CD, some settings are causing the crashings.
2) I put the DLCs in Data folder and had them checked when running the unpatched version of the game. However, the game still crashed when the DLCs were unchecked in FOMM.
3) GFWL is causing this - somehow. I had had FOSE before the uninstall process.

Any help appreciated. My pagefile is ~500 out of ~2800 which is 200m more than when I first installed the game, but that doesn't explain a thing when as I said, till today the game ran fine sans mod-caused crashing.

EDIT: Typos

EDIT2: Could system restore revert the uninstall? I'm sceptical but that would save me from a lot of pain.

When you reinstall have you made sure it's completely clean by deleting the fallout 3 folder left behind by the uninstall, and have you deleted the ini files and things as well?

Have you tried installing just disc 1 and not the dlc?

Can you run the game the instant after an fresh install, no patches or anything?

Ok I deleted the .inis and with launcher made new ones and alas, it works!
Thanks!

I'll have this locked.

As requested. *click*