I've been away for some time due to a winter storm here in North Texas having knocked out my internet (and TV) services, but now all is good!
I had recently purchased an Xfrog volume pack, Oceania 1. Lots of really nicely detailed foliage, but only one specie (all 9 variations) of them that I've found so far does not render properly. Instead of rendering leaves, they come out as black polygons. I checked the image files associated with the colour images and they all look normal. I tried adjusting the translucency and it has no effect. I compared the Default shader settings against one that I know will render and there's no difference. So it must be something with the Object Part nodes, which have no adjustable settings that I can see. I have contacted Xfrog support, but as I now know they are a tad slow in responding. So in the meantime, maybe one of you would have some insight.