I would recommend against keeping System Preferences running but hidden. If you accidentally leave System Preferences running with the Network pane selected, you are running a separate daemon called "NetCfgTool" that is waiting to make changes to your network configuration based on your selections in the preference pane.

"NetCfgTool" only seems to run whenever System Preferences is open and the Network pane is selected; however, in those circumstances it is running regardless of whether or not System Preferences is hidden. I imagine that having this daemon running when other applications may change network configuration settings (or when kernel events could occur, such as the removal of an Ethernet cable, or the disappearance of an Airport network) this could lead to unexpected behavior in System Preferences; finally, this could end up corrupting the "/private/var/db/SystemConfiguration/preferences.xml" file that stores network settings.

Just a thought.

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Lex Talionis

It appears that that daemon launches once the Network panel is opened, and remains active until SysPrefs are closed, no matter what panel you go to after the Network panel. Watch it in Activity Monitor.

True. If I recall correctly, this is not the same behavior as Jaguar. Looks like a bug.

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Lex Talionis