Do the following
At the top of your code, just after the graphics command :o) What this does, is clears all the filters that are preset for textures. In your case, stops the mask flag from being used.
ClearTextureFilters() TextureFilter "",1+8
At the top of your code, just after the graphics command :o) What this does, is clears all the filters that are preset for textures. In your case, stops the mask flag from being used.