I cloned a debian squeeze virtual box vdi and created a new vm using the cloned vdi as the disk. When I booted the vm I found that eth0 had not started. Looking at the logs revealed that it changed interface name to eth0. This was probably due to the new mac address showing up. I had no interest in preserving the old rules. Removing the /etc/udev/rules.d/70-persistent-net.rules file and restarting the vm resolved the issue.