As many here on the forum I had bad performance and random crashes in Fallout NV. This is how I solved it;

http://www.gamesas.com/index.php?/topic/1123460-potential-fix-for-npc-slowdown/page__pid__16519637__st__80&#entry16519637

By adding that dll file discussed I solved the slowdowns.

Funny, to solve the random crashes I had to resort the quad core bug fix I had to apply to Fallout 3. Worked like a charm.

This is a solution that I think was on the old fallout 3 forum, but I will just paste the text here, because I saved it back then (just remember that the paths are a bit different in FNV than FO3 to where you find the files).

QUAD CORE FIX:
Ever since Bethesda came out with the 1.1 patch for Fallout 3, I couldn’t play the game anymore. Once I got into the game and started wandering around, I’d randomly “freeze” up… the video would stop updating, but the sounds/music would still play. Keyboard clicks and mouse clicks did nothing, requiring me to ctrl+alt+del and kill the task manually.
It looked like I was SOL until the next patch, but I found some help online:

The game engine has some issues with processors that have more than 2 cores. You can force the game to only use two of them and it will stop the freezing. I haven't had it freeze once since I did this several days ago.
Open up the fallout.ini file in: My Documents\My Games\Fallout3
Find the line:
bUseThreadedAI=0
change it to:
bUseThreadedAI=1
Add another line after it and insert:
iNumHWThreads=2
This will limit the game to 2 cores and prevent the engine bug from causing the game to freeze.

Surprisingly, this worked like I charm. I do indeed have a quad core processor, so it sounds like this was the culprit. Why 1.1 broke the game for me.. I have no idea. It sounds like Bethesda needs to do some better testing on multi-core processors.

Thanks for posting this. I had forgotten about the quad core fix in the fallout.ini file from Fallout 3. Worked then and appears to be working in NV

I really am surprised that the QA for Obsidian didn't have quad core machines, at least a few of them. It would be a very simple fix for them to add those two lines into a patch file. I have an Intel i5 quad core if that helps the developers.

I'm struggling with the jerky / stuttering, but not quite ready to try downloading dll's

Obsidian, pay attention to this thread, two easy fixes for the next patch.