I recently encountered the following error message while accessing the Network preference pane on my PowerBook G4 running Mac OS X 10.4.11:
“Your network settings have been changed by another application”
What’s characteristic and aggravating about this error message is that it can’t be dismissed by clicking the OK button that appears in the dialog box. The only way to remove the error message is to Force Quit (Command-Option-Esc) System Preferences.
A search on the web revealed that this abnormal system behavior starts to manifest itself after the installation of an Apple Security Update.
Fortunately, the fix is simple: Open the Security pane in System Preferences, and place a check mark in the box labeled, “Require password to unlock each System Preference pane” (this is how it reads in Leopard; wording may be slightly different on Tiger systems).