Here's a cheat that will improve but not eliminate the problem:

In the material room, find the surfaces that exhibit the artifacts; plug the color map into the ambient color node (NB as well as, not instead of the diffuse node) and set the ambient color to white.

Make the Ambient Value very low - something like 0.02 for starters - and do a test. Raise / lower the ambient value until the artifacts are minimised but the wall (or whatever) doesn't look like it's glowing. It's a very fine balancing act, but it saves having to hike up the IDL quality and produce long render times.

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Windows 10 x64 Pro - Intel Xeon E5450 @ 3.00GHz (x2)

PoserPro 11 - Units: Metres

Adobe CC 2017