How about something wrong with the shaders being generated? Can force the game to redo the shaders or better still clear out your current shader cache might be a nice way to make sure ever is reset,
Nividia puts its stuff in: C:\Users\[USERNAME]\AppData\Local\NVIDIA\DXCache
Can also make sure if you have enough shader cache available rather than having to build stuff on the fly, Nividia Control Panel can set a cache size on disk or unlimited
Nividia puts its stuff in: C:\Users\[USERNAME]\AppData\Local\NVIDIA\DXCache
Can also make sure if you have enough shader cache available rather than having to build stuff on the fly, Nividia Control Panel can set a cache size on disk or unlimited