My model is black too, but maybe I am not setting it up right. Let me describe my process.
I texture a model in med. Export to bmp. Open bmap in photoshop. create new channel "Alpha1". select rgb image, copy, and paste over alpha image, which turns it grayscale. save as a .tga. import back into med and apply over original texture. Is that the correct procedure for preparing a model? If not then maybe that is my problem. I have never got bumpmapping, or any shaders to work on models.