This point only apply to a Debian Etch system, not an Ubuntu one. Be aware of that.
If you get an error that looks like this one :
Configuring network interfaces...SIOCSIFADDR: No such device eth0: ERROR while getting interface flags: No such device SIOCSIFNETMASK: No such device SIOCSIFBRDADDR: No such device eth0: ERROR while getting interface flags: No such device eth0: ERROR while getting interface flags: No such device Failed to bring up eth0.
You have to empty a file, so let's simply do :
Then, shutdown your vm, and start it again, and you won't get anymore the error and the network have to work now, so try a simple ping first on your local lan, and then a host on the internet.
At the next startup of the vm, the kernel will put in the file :
the proper setting for your network, I means the mac address of your NIC.