Which Revision of Ubuntu?
I can confirm that 13.10 works fine. There are ALWAYS issues to over come when launching FOG in each environment, everyone has different switches and hardware. I know you want to blame Ubuntu, and I will admit that the latest revision of Ubuntu have needed some adjustment to work perfectly with fog. But I can also confirm that each one of my test servers is at the latest revision. So I don’t think this is a problem with Ubuntu.
I also want to note that I am able to boot, and image to my servers on 13.10, but I am using the Beta version of FOG.