It could also be your material(s), vray with certain types of materials like standard materials or mental ray materials will render pure black. You should make sure you're using vray materials. I think there are some simple scripts that check your scene and convert materials, if they exist they are probably up on…
Here's screenshots; there is one group of objects that does show up for some reason, it has the same material applied as some of the others and the properties don't differ in any way as far as I can tell.