Hi - I have a feeling I have read about a similar problem to the one I am currently having, but I can't now find it in the forum. It is similar to, but not quite the same as, this one:
http://www.jmonkeyengine.com/jmeforum/index.php?topic=6505.0
Anyway, problem is this: I create a scene containing a terrain (sea) with various models (ships) on it, each attached to a DLOD node. The camera is attached to one of the ships. Now if the camera happens to be pointing at the origin of the root node, then all is well and everything appears as it should. But if the camera's initial FOV does not include the origin, then none of the ships (including the one the camera is attached to) appear. Switching on visible bounds, the place of each ship is occupied by a single bounding sphere, but no model under it. Now if I rotate the camera so that the FOV includes the origin, everything pops into view, and thereafter all works perfectly, wherever the camera is pointing.
Sorry this isn't very detailed, but I'm hoping there is a simple obvious thing I should be doing to make this go away…