I disabled all mods so I know that's not the problem. Are there any known fixes for this?

EDIT: I also deleted all local files from steam and re-downloaded the entire game but so far nothing. Any help would be greatly appreciated because this is completely game breaking and is extremely annoying.

Specs:
Windows 7 Home Premium (x64) service pack 1 (build 7601)

2x 1024gb DDR3

3.00 gigahertz Intel Pentium 4
16 Kilobyte primary memory cache
2024 kilobyte secondary memory cache
64-bit ready
Hyper-threaded (2 total)

PNY Nvidia GeForce 9800GT 1gb Driver version 285.62

Any of this help?

Between Fallout3 and Fallout: NV, Obsidian upped the CPU ante to dual core and left you behind.

That CPU is at least six years old, which is beyond obsolete (it was that when new, compared to A64 processors), so you have gotten every penny's worth of use there ever was in it, back out. It's time to move on.

True, but I was able to run the game without this problem for a few days. And at decent settings. I'm building a completely new rig though and I'll be up to speed with a quad core.

Try with an older graphics driver. For this game, and that GPU, you may have been left behind by nVIDIA this time.

Remember, it takes 5-6 years for major changes such as single core to dual core to move from FPS games to RPGs, so Quads are still 2-3 years from implementation, and both Skyrim and DA-2 benefit from having some cores taken out of the game's sight, on some systems.

I'll try it, i'm not sure what good it will do, though. The game started acting up a couple days ago and would crash really often, then it stopped and ran completely fine like Fallout 3 but now instead of crashing randomly it started doing it only when I go to merchants or my companion's inventory. I swear its like the game chooses a new random way to annoy me on a daily schedule. BTW, thanks for the help.

Yeah, no luck with the drivers...

You don't leave your OS wide open to Microsoft's tampering, do you? Letting them have free access to "update" whatever and whenever, is like a license to screw things up! Are you running a thermal monitor? If so, what are the in-game readings for CPU and GPU? P4s could get awfully hot sometimes, and the heat sinks on them filled up with dust rapidly.

Nope and nope. Honestly, my main fan went out about 2 weeks ago and I have the side panel of my case off and I have one of those clip on fans you might would use like in a college dorm room or something blowing into it. Funny thing is that it works a lot better. Hasn't gotten close to the heat I was getting before.. But, I doubt hardware is the issue(this time) because it only happens when I try to buy from merchants. Other than that the game runs just fine.

How does a new game work? Start a new game and try to buy from a merchant.

[censored] on my [censored] and call me Sally, IT WORKED! Too bad I gotta start over though...

You don't necessarily have to start over. Odds are its a bugged item in your inventory. Make a manual save and find a safe place.
Drop everything and start picking things up. If you can sell to the merchant without crashing then keep picking things up until it you crash. It might take some time
but at least you wont have to start over. This issue isn't uncommon especially with mods.