Scientific Linux 6.x EPEL supports cloud-init version 0.7.4. This version of cloud-init has two known issues related to IP assignment to virtual machines (VM).
a) Parse error for ifcfg-eth0 - If the image or snapshot that the VM is being created from has existing static network configuration, cloud-init may not assign it a new IP address due to an error parsing its network interfaces.
The attached update to cloud-init 0.7.4 (cloud-init-0.7.4-2.noarch.rpm) addresses both these issues.
You will need to first uninstall any existing version of cloud-init installed on your VM, before installing the provided rpm. Follow these instructions for that process: