What I can say is that if I play FO3 without installing any DLC and without updating the patches this problem isn't there. So I'm pretty sure it was caused by some patch or DLC...

Problem goes away if I use Bloom.

It also goes away if I play using HDR and disable SLI.

But the solutions are no fun since they involve either not installing DLC's and not updating the game, or using bloom and getting a dull game, or disabling SLI and getting very low fps in my case

So I am hoping that, since this was caused by a patch, perhaps someone from you expert mods here might come up with another patch to correct this

Here's what I'm speaking about:

http://www.youtube.com/watch?v=QZDbZQZcEo0

http://www.youtube.com/watch?v=MZpHnWQHG_I&feature=related

http://www.youtube.com/watch?v=GP7fVivogN0&feature=related

I think this issue started appearing after patch V 1.1