Yes it was an OBJ set to n-gons out of MOI. It also comes in that way if I set MOI to mesh with triangles only, so it's not just n-gons or quads that it freaks out on.

What's odd, is that it works fine for some objects and not others. I think it must get confused with objects that have 'insides' (if that makes sense!)

Look forward to testing the LWO exporter. I have a rendering job to do at the moment with CAD files coming from CATIA, would be great to have it for that!

:D