Poser 6 specific materials and jpg displacement maps: Poser 6 cannot read the 16-bits displacement maps properly; you will need to download the following file and install it alongside the original set.
These are materials for Poser 6 (they will work in Poser 5 but things like Ambient Oclussion node will not work). Just unzip the file into the same runtime you've installed Jack of Hearts. It will install a new folder with P6 materials, and jpg versions of the original png displacements. If you use P7+, use the materials provided originally instead.