I guess I'm a dinosaur here but I've been using Datacad 10 for years and then all of a sudden I cannot export to dxf or dwg correctly. When I export all my layer get transfered into one layer on the new file. All the information is there, but it all in the same layer. What did I do. I reinstalled Datacad with no change.
DataCad has been exporting to layers with no problems for a lot longer than ten years.
Are you looking at the exports with some other programme? If so, have a look at it with DataCad and check that the layers are kosher. If they are, you know where to point the finger.