[PROBLEM]
You've configured your network using gnome's "network-admin" tool (The one you get when configuring your network over the "Network Monitor Applet" e.g. in Ubuntu), but one of your NICs has changed and you'd like to apply this to ALL of your previously stored profiles.
In my case, I bought a new WLAN adapter - and ended up with profiles for "wlan0", but had "ath0" now.
[SOLUTION]
Thanks to a posting in a forum, I finally found out where the actual config file is:
/etc/gnome-system-tools/network/profiles.xml
Here you can freely edit (aaah. finally!) things. Good luck!