When I switch to Raytrace view I have an object that disappears ? Its a closed poly surface which was modelled with Sub-D tools and then changed to nurbs ??
Can you please share the file with me? For confidential sharing you can use rhino3d.com/upload?to=nathan@mcneel.com . Thanks.
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Hi Nathan, sent 
Nathan, just to add, I originally modelled this scene in Rhino Mac V7 WIP. I was having trouble with snapshots and materials so saved it back to V6 Mac, and continued working from there, not sure if this has anything to do with the issue. I just checked the original file which is still V7 version, and the object doesn’t disappear when switching to Raytraced ?? 
Probably something with saving as v6 messed with the material. Create a new custom material and assign it the texture the original blue fabric material has. Then assign that material to the sofa and voilá.
yep, definitely something to do with materials and snapshots. Changed the material as suggested it now displays ok in Raytraced , cheers