Actually if you run the DX11 exe with a DX10 card in Vista or Windows 7 then it defaults to DX10 mode, so just without the tesselation on the aliens really.
I have the same problem The same thing happens with one of the decompilers I think it's because of windows 7-64 bit's drivers. They seem to be incompatible.
Additionally just reducing the material size for each mesh in Unity. where is shows the 7 materials, causes parts of the mesh to go invisible from the scene.