I'm probably describing the problem of the trees becoming unglued improperly. In the file with the forest objects, the forest objects are attached (linked) to surfaces in the same file. There is no xrefing going on in the forest file. What happens is that after i render the view file with the xref'd forest file in it and then close it, i then open the file with the forest objects and find that some of them have become unglued, not all of them. I then have to shut down max and then restart it, then open the file with the forest objects in it and magically they are back to being glued to the surfaces. Not a big deal, just a minor irritation.