Hi Bob, well the first thing I'd recommend is trying MoI v3 and see if it works any better. You can get the 30-day trial version from here: http://moi3d.com/download.htm . There were numerous fixes in v3 to all sorts of things.

If that doesn't do any better then it's probably related to something in the structure of these particular objects, if one of the objects contains any degenerate surfaces in it (meaning surfaces collapsed down to just a thin sliver with no real surface area to it), or degenerate trimming boundaries (edges that do some kind of loop-de-loop crossing over themselves), then that can cause problems with mechanisms that try to analyze what volumes things are contained inside of.

I could probably give you better information if I could examine your model file, can you post the 3DM file as a file attachment here or e-mail it to me at moi@moi3d.com if you want to keep it private?

- Michael