Se deparar com erros na hora de configurar uma placa de rede no Linux não é uma coisa comum, e geralmente quando acontece, a solução é simples.

Estou testando o Fedora 13 e me deparei com o erro abaixo:
Shutting down interface Lan: Device state: 3 (disconnected)
[ OK ]
Shutting down loopback interface: Error org.freedesktop.NetworkManagerSettings.InvalidConn ection: ifcfg file ‘/etc/sysconfig/network-scripts/ifcfg-lo’ unknown
Error org.freedesktop.NetworkManagerSettings.InvalidConn ection: ifcfg file ‘/etc/sysconfig/network-scripts/ifcfg-lo’ unknown
Error org.freedesktop.NetworkManagerSettings.InvalidConn ection: ifcfg file ‘/etc/sysconfig/network-scripts/ifcfg-lo’ unknown
Error org.freedesktop.NetworkManagerSettings.InvalidConn ection: ifcfg file ‘/etc/sysconfig/network-scripts/ifcfg-lo’ unknown
[ OK ]
Bringing up loopback interface: Error org.freedesktop.NetworkManagerSettings.InvalidConn ection: ifcfg file ‘/etc/sysconfig/network-scripts/ifcfg-lo’ unknown
Error org.freedesktop.NetworkManagerSettings.InvalidConn ection: ifcfg file ‘/etc/sysconfig/network-scripts/ifcfg-lo’ unknown
Error org.freedesktop.NetworkManagerSettings.InvalidConn ection: ifcfg file ‘/etc/sysconfig/network-scripts/ifcfg-lo’ unknown
Error org.freedesktop.NetworkManagerSettings.InvalidConn ection: ifcfg file ‘/etc/sysconfig/network-scripts/ifcfg-lo’ unknown
[ OK ]
Bringing up interface Lan: Active connection state: activated
Active connection path: /org/freedesktop/NetworkManager/ActiveConnection/2
[ OK ]
Bringing up interface Reliance: Error: Connection activation failed: Device not managed by NetworkManager
[FAILED]

Apesar do erro ser bizarramente grande, basta alguns comando para sanar o problema:

1. chkconfig NetworkManager off
2. chkconfig network on
3. service NetworkManager stop
4. service network start