OS 10.4 - Print & Fax Prefs don't stay locked

On a 24" iMac, sudden change in printing 11x17 from a CAD application. Always worked til last week. 11x17 prints OK in a different CAD application, and in Word, and in Excel. Troubleshooting finds that Print & Fax Preferences settings don't get grayed out when the padlock is closed, and they don't stay locked after shutdown.

Next boot, the Print & Fax Preferences padlock is open, and the saved AppleTalk printer are gone. Network prefs show AppleTalk enabled, but must go to Terminal and enter "sudo appletalk -u en0". Response is "current zone for interface en0 is *". Then the AppleTalk printers will appear in the Printer Browser.

That AppleTalk setting from Terminal is lost at shutdown. Next boot, AppleTalk has to be reset from Terminal.

Any ideas welcome! Thanks.