After an update on 13.10, my PC won't boot Ubuntu any longer. It displays the infamous "Waiting for Network Configuration" message and then hangs. I can go into recovery mode, and choose "Start networking" and then go to a root prompt, and that works fine. Ping works. /etc/network/interfaces contains just the two lines "auto lo" and "iface lo inet loopback". I've double-checked that my network is working, the cable is working (it works on another PC) and the network card seems to indicate a connection. Any suggestions on how to get my PC booted again? Right now I'm limited to a root shell prompt.