The image above shows the UVMapper results (none too good, I know) and the Poser preview results of an object I have modeled as part of an outfit.
The result in the Poser preview window is what I expect. The skull image is a simple black/white image map.

If anyone knows what's wrong here, please let me know!

try turning global smoothing off (use local smoothing per obj if needed) and see what happens

Smoothing is not the problem. This happens with smoothing on or off, both global and per object.

actually smoothing can cause this, so thats why I asked ;)

can we see the mesh?

It renders fine in the Poser 4 render engine, by the way.

It may be that S.T.O.M.P. mauled the .OBJ file. I'm going to try from the pre-STOMPed base objects

Can we have a look on the shader node?
Or pack the prop and send it to me (adp at elizadigital.de). I would be glad to look over it.

normals forward? we can see the mesh in the uvmapper image - it's a disk made of quad polygons. almost as if none of the quads is welded to each other

The bad quality of the UVmapper image is due to the screwing up of UV coordinates by 3DS Max.
The quads of the .OBJ are cleanly welded.
Normals forward does not help, I checked.

is this a small piece? like a broach or button or something?

if you turn off the shadows does it look ok?

if so. put something else in the scene. a person or prop anything.

Weird. Just a thought but could it be double sided polys?

Without shadows it looks OK.
I'm going to check for double sided polys

Quote - Without shadows it looks OK.
I'm going to check for double sided polys

Try increasing the "Shadow Bias" for any lights you have casting shadows.
If the object is small, then if changing the Bias isn't having any affect, make the object 10x larger and see if the situation improves.

The object is not very small in Poser terms - it is one of the cups of an armored bra.

I checked something else too. The cup was exported as a poly from Max. I converted it to a mesh before exporting, and that seems to help.

I assume you tried resaving the OBJ from UV mapper?

I run into a problem a couple times when the Max exporter did something strange and this fixed it.

The editable poly was the problem. The new export renders as it should.