With Ubuntu 11.10 server, 2 ethernet interfaces, eth0 and eth1. Don't know what caused the eth0 became unmanaged via System Settings --> Network ? (eth1 is configurable though) this caused that the eth0 was unable to re-configure via System Settings --> Network GUI ! it can be re-configure via command line i.e. ifconfig though. Anyone know why and how to fix it within the Network GUI ?