Hey, I've got a similar yet different problem. I've got a model of a tank (body, turret, barrel), and in MED all the normals are right, I've imported/exported it through Milkshape replacing the textures, I've tried it in MED with skins with and without alpha channels, I've set my.alpha to 0 and 100, whichever is opaque, and I still get the transparency.

As you can see from the below pics, the middle of the body is transparent - the opposite wheel is clearly visible - the turret, although it has the same skin as the body, is darker and transparent to the barrel, and the barrel has an ugly joint in the middle.

What it should look like - screenshot from MED
What it does look like... - screenshot from in the engine

I don't claim to be any good at modelling/level design, I'm more intrigued by the scripting, but I'd like to be able to make at least simple models that can get me through, at least to test the scripts without creating more problems. Any help would be very much appreciated.