It seems that (some of) the plugins won't work on 16 bit RGB. Converting images to 8 bit RGB solves the problem.

FWIW - I find it frustrating that PSP won't truly handle 16 bit RGB. My other main photo tool Is Picture WIndow Pro, and it doesn't support plugins. I'd hate at some point to chuck these all and start using Photoshop (not likely as I love PWP - although for production work and web work PSP is much better).

I'd love to know what Corel intends to do with PSP. X seems to be neither fish nor fowl. The new "manual" seems designed for the casual (big market) family photographer as do the retouching tools. At least they still support scripting...