I know this problem. It arrises when AutoCAD cannot find the TGA image files in the TEXTURES folder. Many of the AutoCAD materials use an image texture. If the texture is not found, the object is rendered black. The solution is to make sure that all the TGA files are in the textures folder. I think that a "minimum" install of AutoCAD does not include them. This is the same problem you have with the materials. There's no need to do a reinstall. Simply find one of your PCs that has the full compliament of materials and copy the contents of the textures folder to those PCs that have only 4 materials.
Let me know how you get on.