Comment 3 for bug 157479

Had the same problem. I upgraded from feisty and the network-manager behaviour changed.

Make shure that all interfaces in /etc/network/interfaces are commented out (except for lo).

auto lo
iface lo inet loopback

#auto eth0
#iface eth0 inet dhcp

#auto eth1
#iface eth1 inet dhcp

Is this you problem, too?

Jan