Millighost - So far as the light source, that seems to affect which side of model the odd effect appears on but doesn't otherwise affect it, its always whatever side has the strongest light source.  So if the strong light is on the left, it appears on the left, move it to the right, the effect follows to the right side.  I'm not entirely sure why but I have a theory (see below).  I have not tried it with no light source.

I'm not sure what size the polygons are in Poser terms, there are a wide variety of sizes in the overall mesh (which you can see from the UV Map, which btw I've replaced with a new one after changing the mesh to get rid of a few polygons trying to clear this issue up).  But in the area that seems affected all the polygons are relatively large (some of the largest in the mesh).

Are you saying the location / distance of the polygons relative to the origin matters?  So far as the location of the prop, I've seen this occur no matter where in the scene the prop was placed.  But yes I think it would be easy to edit the origin point though I don't wish to since I think that would make placement awkward.

Now for my theory... and its just that based on what I've observed.

The part of the node that seems to be causing the problem is the Scale in the Granite node.  Changing any other part of the node or other nodes may change the material appearance but doesn't cure or cause problems, setting Scale to 0.75 or more (I didn't try past setting it to 1) clears it up completely.  After a bit of reading I learned that this particular function determines the size of a small speckle color, which in the default MAT is the pink color.  These are then scattered about according to the rules of the Granite node.  The color itself doesn't matter, I can change it to blue and get a blue color error, green and it turns green, etc.  I'm assuming that since this speckle is probably multiplied with/by the light during render, and because they are too small, it cause the problem.

I've noticed that the material as it appears in the Material Room versus its appearance on the wall is quite different.  In the Material Room the distortions that are supposed to simulate marble veins (and it does it pretty poorly in my opinion) are much larger in the Material Room than on the wall itself when rendered.  I'm not entirely sure why this is or how to go about fixing it.  For some reason the Marble MAT seems to be "tiled" very small on the wall.   As a result those pink "spots" are probably so small the Firefly engine can't render them properly and runs into the same issue that causes the strange shadow effect with very small props (this flaw in Firefly seems to be becoming the bane of my Poser existence, so to speak).

That's my best guess at the moment.

The solution would be to scale the whole MAT effect up, but I don't know how to do this.  There doesn't seem to be any node I can add that would just control the scaling (rather a silly thing for them to overlook when making the material nodes).  Likewise, the default Brick MAT that came with Poser 6 renders correctly but the bricks are HUGE on the same wall area, fortunately that one I can scale down.

So it appears the root of my problem is a scaling issue and I'm not sure how to go about fixing this.   How do I tell Poser to scale applied MATs in some uniform way?  Texture maps work just fine and have no problems, but some material files seem to have scaling issues, others do not.

I'm all ears for suggestions on this one.  For the time being I'm limited to Poser 6, and for sake of backwards compatability I want to solve it for that version forward.  But dear god I hope Poser 10 / Pro 2014 handles this better! LOL

Otherwise the only thing I know to do at this point is continue with the project, stick with the intended texture maps (which will look far and away better than these MATs, I'm not actually planning to use MATs and ran into this purely by accident) and include a note in the documentation that some MAT files may not work properly with the props.

Course that annoys me, they SHOULD work and the fact they don't bugs me.  I have no such problems in Blender where the equivalent of MATs render beautifully.  So.... Firefly sucks... there, I said it... I'm glad I said it.  LOL  (Appologies to Joss Wheadon, not THAT Firefly.)

Again, thanks for the input and suggestions, not sure I'd have gotten this far without it and if nothing else I'm learning things about how Poser works that I didn't know.