I have been running Lubuntu 12.10 successfully for several weeks. Today it refuses to connect to the Internet stating in a dialog box immediately after logging in that 'Network Disconnected You are now off line'. Apart from this lack of an internet connection, it seems to be running normally.

The Lubuntu 12.10 is running as a guest in Virtualbox with Ubuntu 10.04 as the host. The host can connect to the internet successfully. I quickly created another Lubuntu 12.10 virtual machine and confirmed that it can connect to the internet and that the virtualbox settings are the same - they were.

No changes have been made to the networking settings so I have no idea why it should suddenly stop working. Any suggestions please?