I'm having similair problems with Poser Pro and never had them in Poser 6. Some external runtimes are fine, while others give problems. I've found a simple solution to the problem, I've copied all the textures from the runtimes that gave problems to the main Poser Pro runtime folder and now the problem is gone, since that's the first place Poser Pro looks for textures when having problems.

Artwork and 3DToons items, create the perfect place for you toon and other figures!

http://www.renderosity.com/mod/bcs/index.php?vendor=23722

Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk