download and install 275.27, it's the most up to date working driver, if you want to turn motion blur off completely or are having other problems give it a go>>

http://www.nvidia.com/Download/Find.aspx?lang=en-us

275.33 was released the same day as patch 1.8, so the driver's probably not been tested with the new C2 1.8 and that's what caused the problem with the weapon going all blurry and is probably causing the other weapon problem of disappearing completely.