You need to patch Poser 4. I've the same problem with my new computer and now it's ok with poser 4. Go to http://www.curiouslabs.com/downloads/index.html

The link : http://carrarastudio.com/tutorials/littleplanet/part6/

Go to carrara studio site. In the tutorial taket the little planet. You can found what you want in the part 6 of the tutorial. It's an explanation on how to build a tree like a sprite with transparency. I try it an it's very good. Vince.

I've not the PB, but I'm working with Win XP pro.