Hi TimTab, there are certain kinds of anomalies like trim boundaries that have self-intersecting loops
in them and similar stuff that can cause stuff like you are describing. Those kinds of things can cause
various operations to fail including generation of display meshes.

An object will be of type "Solid" if all of its edges are joined between 2 surfaces and there are no
unjoined "naked" edges in it.

If you can send me the model file at moi@moi3d.com I can take a look, there might be a couple of faces
in there with malformed trim boundaries that need to be repaired.

- Michael