I don't know, we don't have access to your PowerBook to see if it's loose or not -- you're going to have to tell us whether it's loose or not.
If it is loose, then you've got plenty of options if it's still under warranty (you did purchase AppleCare, right?). If it's not under warranty, well, you're going to have to be a lot more specific if you want us to diagnose anything -- are the hinges loose? Or does the screen twist side-to-side? Does it close or fall open under its own weight? Is it just a matter of the LCD not caring who it's intimate with?