Ok, with regard to my crashes and white screens:

Every time I see a merchant and spend a HEAP of caps or receive a HEAP of caps I'm pretty much guaranteed a white screen if not crash. When I exit the Barter screen the FPS goes from 60 to 7. Then bam. It seems that caps are all object instances rather than the quantity being a global attribute of the object. I'm not really sure because this doesn't hold true for the cash exchange at the casinos. With merchants if I spend under 200 caps or receive under 200 then there's barely a frame rate drop. If I do more then... as above. If I exchange a lot of items, same thing. Easily repeatable if you TGM. Cheats aren't needed to repeat this though.

So if I exchange a lot of caps or items I most certainly crash a lot when going back to the NPC Dialog.

Edit: F5 is my godess! I estimate near 300 crashes or white screens, crashes 30%. I'll actually start counting from today and post a 7 day crash or white screen count. I truly believe they are different though.

I too have noticed crashing when clicking the accept button for bartering. It also happens to be after I have meticulously gone through my inventory and is usually a fair sum of caps. I just thought it was conincidence.

Chalk one up for my long list of stuff that makes my game CTD.

I have a similar problem, whenever I sell stuff to a merchant, buy stuff from a merchant, or give items to an object in game (like a footlocker, wardrobe, or one of my companions) I usually get a CTD, or if i'm lucky the screen will just turn black for a couple seconds then go back to the game. Either way, this is a horrifying bug and it's caused me so much grief that I feel like pulling my hair out. If anyone has a solution to this problem, I would absolutely LOVE to know.

Edit: Also, just for informational purposes I run Windows 7, 64 bit.
Geforce GTX 285 video card
4 GB of RAM
Quad-core AMD Phenom II X4 965 Processor

Hope you guys don't have any Playing Cards in your inventory (especially the ones from big casinos).
Getting rid of all of them stopped my merchant troubles and crash-on-save... they're bugged.
Hope this helps,
Regards