I’ve been running very minimal server installs under KVM to experiment with different web services.  As a result I rely on /etc/init.d/network to handle networking.  After cloning a guest in virt-manager on Fedora 12, networking does not work on the cloned guest.  Here are the steps to get back in business:

1) Edit the file /etc/sysconfig/network-scripts/ifcfg-eth0 (or whatever your network adapter is) to reflect the new MAC address of the new virtual network card. The new MAC address can be found under the Information icon in virt-manager for the guest you are working with.

2) Delete the file and rm /etc/udev/rules.d/70-persistent-net.rules

3) Reboot the guest

This is a known issue being tracked as bug 524269.  The cloning feature is great.  Someday I hope we have similar snap-shotting functionality like VMware Workstation and VirtualBox.

Thanks to Sven Lankes Tom Horsley on the Fedora virtualization list for helping me out.