Everytime I press a number key to select a weapon, the moment I left click to change NS exits to my desktop. It only started happening last night.

I've tried loading up DoD and I can change weapons fine.

The first time it had happened I had been pressing a weird key combination involving ctrl+e. It can't be some Windows hotkey activation since DoD works fine...

try this, rebind your slot 1-4 weapons to other keys (e.g. h,j,k,l). then go into NS hit k,j,h,l, if it still crashes then it's NS related problem if not then it must be a windows hot key problem.

secondly try reinstalling NS (+ dont copy over your config.cfg file)

yeah, almost seems like it's calling nonexistent/corrupt model files for weapons, or something.

try the above, but if what I said is true, re-install.