Be sure that you typed exactly the command and the shader's name.
Plus, you have to have the shaders enabled.
When loading a mod, you have to type every letter right. That means if the mod was TwinSwords4.tbm, you have to type it like that, not like twinswords4.tbm.
I wouldn't be surprised if that applied the world shaders as well.
@BladeNinja: If the graphics card can't support a world shader, AFAIK the graphics will turn off the shaders or Toribash will crash.
EDIT: Also, that is an issue that should be posted in Support instead of here, next time you could remember that.