So, as the title say I am having lots of problems with my game.
Last month i buyed a geforce 9800gt because I had a 8400gs and it wasn't good. So yesterday I thougth about downloading new vegas through steam again just to see how it runs on my pc now.
It finished downloading today and I played the game. Fine, it was running ok with settings on ultra and everything, but after ten minutes playing I saw I had not buyed OWB yet, so I buyed it and waited for the download finishing.
It turns ou that after finishing the download the game crashes now and then and my laser pistol doesn't fire anymore. First I thougth that it was an OWB problem, but even when i uncheck it on FOMM it stills keep with the same problem.
The only mod I have is the DarnUI.
Please, anyone help. I can't get past the tutorial without it crashing.

p.s: sorry if there is something wrong, english isn't my first language.

Edit: As I finished writing this I decided to start a new game, when I saw that the problem is not my laser pistol, but all weapons except my caravan pack shotgun. And other thing that is happening is that after activating OWB again, I went to do the quest, just to see that everything in the scene added by the dlc was big red marker, as if there were no meshes from the dlc.
Please, help me. I really want to play this game more. The 400+ hour I have played just aren't enough.