I have seen this many times for different reasons. I would say the most common with FOG is that when you built the golden image, you did not disable the FOG Service according to the wiki page. Then the fog service should be started in the setupcomplete.cmd batch file.
You will get this error above under several conditions, the most common is the target computer rebooting unexpectedly during WinSetup/OOBE stage. If the FOG client is left running when the image is captured. When deployed the FOG Client will start working before OOBE has finished. Part of the FOG Client’s job is to rename the target computer and reboot. If this happens during OOBE you will get the above error because of the unexpected (to OOBE) reboot.
Other places I’ve seen this is if a bad driver is installed causing the target computer to reboot before OOBE is finished.
If either of these are not your case there is additional debugging you can do, but lets not go into that unless its needed.