Existing users, 
VERY BAD UPDATE. DO NOT INSTALL.
If you have not already installed "Security Update 2008-006," DO NOT INSTALL IT, especially if you are using a laptop and change "Locations" often! Thousands and thousands of OS X 10.4.11 users are finding it impossible to use the Network preference pane after applying this update. There is no fix from Apple at this time, and although there are some work-arounds. Mostly it breaks your system.
VERY BAD UPDATE. DO NOT INSTALL.
Apple Security Update
for PPC OS X 10.4.11
Version: 2008-008
"Your network settings have been changed by another application"
Feedback Type: Review
Contributed by: younkint Thursday, September 25 2008 @ 11:43 AM PDT
Product Platform: MacOSX
Used Product For: Less than a month
Recommend Product: NO
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Comments
"Your network settings have been changed by another application" - Ras-x
This had me pulling the roots of my hair out - affecting both my Powermac and Powerbook. Wish I could claim this was my discovery, as it's a very simple (partial) solution. It does not fix the problem - BUT, it overcomes it.Just go into sys preferences, then click on security, then click on require password to unlock each secure system preference. Voila, no more loopy message! :)
Saturday, November 01 2008 @ 09:21 PM PDT
"Your network settings have been changed by another application" - Net--2008
Yes, I had same problem. Even before, after applying 2008-06 update.To fix this just delete files from Library/Preferences/SystemConfiguration
com.apple.airport.preferences.plist
NetworkInterfaces.plist
preferences.plist
com.apple.nat.plist
Then reboot. But remember network settings you had, cause you will need to set up them again. At first you can move them to Desktop and later open in TextEdit for reference. After that, just delete this preferences.
Friday, October 10 2008 @ 05:50 PM PDT
"Your network settings have been changed by another application" - marcel987P
Removing the different pref files worked for me. Resetting my PPoE Network info for Internet access was fine; however now, even though I asked for saving my internet password and the Internet Connect panel shows dots in the password space, it's like nothing is there, because I have to replace each time the dots with my password. Passwords cannot be saved anymore. Any suggestions? Thanks.Saturday, November 29 2008 @ 09:29 PM PST
"Your network settings have been changed by another application" - barryaus
I got this problem with the last security update. i was hoping that this would ameliorate the problem. I was able to fix it with a lot of clicking and hitting return. I took my PowerBook to the Apple Store and they fixed it. I then did what they did on my desktop machine (harder to lug than the PowerBook)Reply to This
Friday, October 10 2008 @ 12:11 PM PDT