Changes in Ubuntu 12 cause TFTP daemon to try to start before the LAN interface has been initialized. Simply restarting the tftpd after booting the FOG server, or searching the forums for the many topics on tftp problems in Ubuntu 12, you’ll find a modification to the boot scripts that pauses tftpd long enough to allow the interface to be bound to it’s IP before starting.
If you want your hosts to have specific names, use the full registration and inventory option. Quick reg just numbers them sequentially I believe and if you have the fog client configured to rename hosts or join them to AD it may lead to more work than you want.