Someone else would have to tackle that one. I don't use "system-config-network" and I'm not sure if that's what you call Network Manager or not.
NetworkManager is a different beast than system-config-network but both will make changes to your hand-edited configuration files and are best avoided if you want to set up your network the "old fashioned" way.
See http://people.redhat.com/dcbw/NetworkManager/ for an intro to NetworkManager.
Paul.
