Changing Texture at runtime

Hello! I am trying to change the texture of a person at runtime from a normal shirt, to a bloody shirt. (I am using a texture map) In the editor I am able to set the texture just fine (the texture map wraps around properly) but at runtime I use renderer.material.mainTexture = wwwdownload.texture; which works fine for normal textures, but for texture maps it doesnt map it. Kinda stumped on this one. Any ideas/help would be appreciated! --Ben