Network manager can only run an interface that does exist. If you have any configured interfaces in /etc/network/interfaces then network manager can do nothing with it. Try commenting out any lines that are in this file and see if it repairs the fault.
This is how mine currently looks and network manager is using my network interfaces perfectly. auto lo iface lo inet loopback auto eth0 iface eth0 inet dhcp auto eth1 iface eth1 inet dhcp auto eth2 iface eth2 inet dhcp auto ath0 iface ath0 inet dhcp auto wlan0 iface wlan0 inet dhcp -- NetworkManager does not recognise any interface after upgrade to 2.6.20-7 https://launchpad.net/bugs/84307 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
