Comment 8 for bug 500520

For some reason i didn't have loopback interface defined in:
/etc/network/interfaces
So i've done:
sudo vim /etc/network/interfaces

and added:

auto lo
iface lo inet loopback

I think Ubuntu should have some self testing tool for basic settings. If it is known that some apps do require loopback interface for working (e.g. upstart) then there should be some automatic test tool checking whether the interface exists !! Ther should be some general solution for this kind. Maybe some kind of 'Unit test' tool