If you are trying to figure out how to get your network working again after cloning a VMWare image from Ubuntu 8.04, I hope you find this post before you waste an hour trying to figure it out like I did.
After copying the VMWare files and launching the copied instance be sure to tell VMWare that you copied the image. This will generate a new MAC address for your cloned server. You will need to remove the networking udev rule though, in order for udev to figure out your new MAC address.
Just run this command:
sudo rm -rf /etc/udev/rules.d/70-persistent-net.rules
If you keep a base install image on hand (highly recommended!), be sure to remove that file before you start to make copies from it. Then you won't run into this problem again!