I installed the auto software update for HP printer software on the latest 10.5.6 version of Leopard.
Strange but it overwrites the installed raster driver which then is damaged according to the print driver dialogue.
The new version has most of the print set up for generic printing, but is missing things like gloss enhancer, color options etc.
Easy to fix, download the 3.1 driver from HP , reinstall, and all is well again.
I have no idea if this will overwrite the Z3100 driver as well, post back here if so.