Network settings lost

In the last week i have had to use Network Assistant Diagnostics to reconnect to the internet 3 times. All my other devices remain connected, iPhones x 2, iPad and my wife's Mac Book Pro. After the process of restarting my DSL Modem and WiFi router I am notified that "Your Network Settings have Changed". After clicking OK I am back online. I haven't changed anything so what's going on? This has never happened before so I stymied.

Which device are you having the issues on?

Lost internet setings

Late 2009 MacBook running Mountain Lion.

What gives you the message "Your Network Settings have Changed" ?

I'd start by resetting your network settings. This will remove any old network config/locations etc. So you will have to re-enter your wifi key once it's done

In Finder go to:
yourMacHD/Library/Preferences/SystemConfiguration/preferences.plist

Rename the preferences.plist to preferences.old

Restart your Mac

Attempt to reconnect to your network and try again

If that doesn't work then do the same thing but for the whole SystemConfiguration folder that the above plist is in.

OK, I will give that a try and get back with the results.
Thanks,