Comment 2 for bug 507546

I should also add: because in my testing I was alternating among the "old fashioned" /etc/network/interfaces, network manager, and wicd, I had turned off the "old fashioned" style by simply deleting /etc/network/interfaces. Network manager still configures lo properly in that case, but seemingly wicd does not. It seems one must have this line:

auto lo iface lo inet loopback

in the /etc/network/interfaces as described here: http://www.linuxplanet.com/linuxplanet/tutorials/6527/1/.