I came across this problem a while ago ( http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2787184 - the initial topic was rather vague, but quickly focussed on double-sided polygons).

"Normals Forward" didn't resolve the problem, although it did have an effect - pictures 6 and 7 in my post at the end of the other thread hopefully explain the effect better than my words could!

Using a displacement map to separate the faces was also suggested, but I didn't get round to trying that.

I also had the same strange Poser render artefacts when I accidentally created two duplicate faces (in this case DAZ|Studio also had render artefacts).

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The 3Dcheapskate* occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.

*also available in ShareCG, DAZ, and HiveWire3D flavours (the DeviantArt and CGBytes flavour have been discontinued).