Okay I take it back I am familiar with this issuse.
Its most likly a case of conflicting mods.
Try using Boss, NVedit or manually unchecking and checking mods in your mod manager.
Its hassle to do it manually but try unchecking recent mods you downloaded and you should find which one is being the pain in the butt.
"Now go! Let the Legend come back to life
— Revolver Ocelot