I had no problems installing the Pentax browser and lab software on either of my G4 Macs running OSX 10.4.11. Don't use either hardly at all, but they're there in case I want to take advantage of their different features from my usual Adobe workflow.
Anyway, sounds as though you might have gotten a bad install CD. You might try Pentax customer support, either by calling the service department at the U.S. headquarters at (800) 877-0155, or use the customer support links on their website at
Pentax Imaging. Good luck!