That is strange. Is it possible to upload the scene, or at least enough of it to check out whats going on?
Edit: Never mind that. I just thought of something. If your scene is enveloped by geometry and then you need a value that isn't zero for the max distance on the AO node, otherwise the geometry enclosing the scene will occlude everything.
Last edited by Gen; 09-04-2013 at 07:58 PM.