Edited IPv6 settings for 'Wired Connection' to enabled dhcpv6. Address was acquired but system was trying to route ipv6 via dev lo
To try and make sure routes got refreshed, clicked 'Disconnect' in the Network manager tray applet, click 'Connect' then didn't do anything.
Rebooted and the interface doesn't even appear in the tray applet at all now. Can see it in the NM settings and all looks fine.
Tried removing the ethernet cable and then reconnecting, got
Jul 24 14:34:09 milleniumfalcon NetworkManager: <info> Unmanaged Device found; state CONNECTED forced. (see http://bugs.launchpad.net/bugs/191889)
Bringing up manually works
root@milleniumfalcon:~# ifconfig eth0 up
root@milleniumfalcon:~# dhclient eth0
So should at least be able to use some google-fu