I figured out how to get rid of the error! But I still don't fully understand why I was getting it. I think it was because I had all my Preview Render settings maxed out, and when I reduced them I have not had any further issues. All I can think of is maybe Poser was struggling to display complex shaders made up of many maps in the Preview window, but even then my system resources were far from taxed so I don't see how that was an issue. It worked though which I guess is the important thing.

Thank you everyone!