Hi Brian,

> Curiously, both the FBX files open fine, and checker nicely,
> in Carrara6Pro and not in 3D Coat?

It looks like 3D Coat does not like to handle the n-gons. It is probably set up more intending that your object will be diced up into smaller more evenly sized polygon bits similar to what ZBrush wants.

So that's not really too surprising, you would want to use export settings more like this:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1549.4
when going to a brush based system like 3D Coat, ZBrush, or Mudbox, and use the Quads & Triangles setting instead of n-gons - in this test I did not set up the mesh export settings to do this style of mesh.

- Michael