Comment 36 for bug 50099

I have the same problem in a fresh install of Gutsy, final release...
I totally uninstalled network-manager because I don't need it at all (I have only an ethernet interface, statically configured) and because the loopback interface was not automatically brought up.
Now eth0 is not brought up too...

ghost@Ubuntu:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback

iface eth0 inet static
address 192.168.1.2
netmask 255.255.255.0
gateway 192.168.1.1
auto eth0