SophiD:

This problem seems to occure for several reasons. I believe in most cases, the material nodes get loaded, but without the textures.

In the Advanced Material Room, click on the name of a texture, and in the dialogue box, click on the texture name with the down arrow on its left. A menu of pathway names to textures should open up. Scroll down to the pathway with a blue check mark beside it. Check to see if any of the directory names in the pathway are corrupted. Generally the first letter of the directory name is missing.

In my case this happens when the directory before the "...runtime..." directory contains a number (except at the end of the directory name). A directory name such as "...Poser7..." is okay to use, but not "...V4Cloths...". I have been able to manually load the textures, and Poser could then find them and render, so, your problem is a little different than mine.

lmk

Probably edited for spelling, grammer, punctuation, or typos.