Hi Rich !
Don't know what happened to my previous reply, so here it is again:
It is a problem with importing exported from SU DAE, 3DS and DXF files into Blender and 3DC, I have also asked a question about in their forums.
A SU member suggested trying to re-import them into SU which worked but not at the same quality as their SU originals.
Before I spend £ 330 I must be sure that it does what I want to use if for !
Having tried to buy it before am being told by it's web site forms that a page can not be found, which a support person tells me is a known to them problem with IE8 and would I try using another web browser ?
They must be joking, having to do that just to buy SU-8 Pro !!!
Was hoping that somebody else here could shed some light on why it is not working while I wait for an answer elsewhere.
I just HATE advertising and have it turned off wherever possible, being of no interest to me and an intrusion into what I am doing on-line ! 
The same when watching TV, turning off the sound when they show !
O t t o