My daughter just called with the "Your network settings have been changed by another application" message. We went through this fix. If you have multiple locations you will need to have a paper copy of all the settings for each location you have; 3x5 cards are wonderful for this. To begin restart with the Shift key down. When the computer restarts it will be in Safe Boot mode. Open the System Preferences. Open the Network preferences. Keep clicking OK to the message and get to Edit Locations menu. Create a new location. Name it what you like but do not duplicate a name; you can always go back and rename it. Then delete all the other locations. Restart the computer as you normally would. The Network settings are like new again with only the one you just created. You will have to go in and setup the Network settings manually. If you are using Airport you may have to turn Airport on again and go from there.
I'm not one to jump on every upgrade band-wagon, but a friend had Life '06, and I was specifically after an upgrade to iPhoto. Despite that being a REALLY bad idea, it let loose that '"Your network settings have been changed by another application" which you mentioned/replied to all those months ago. Just to let you know, after DAMNING the machine, my friend, the software etc. for MONTHS, your fix, well, fixed it. Now, I have to ask .. WHY did you do it?! How did it solve the loop?
Yes, I'm at OSX 10.4.11, which would appear to be why everyone else has the problem, but .. it's just rather odd. All the other suggestions of fixes by other users (OK, I agree it was caused by software, so likely to require a software fix) were saying browser/internet setting changes. Yours seemed to be the only one that addresses a PREFERENCE problem. Many thanks. Claudia