I realize it is pretty straight forward but I think it might help other who are having trouble. VirtualBox is still not perfect in the linux guest arena but its gotten a lot better over the past year since Sun apparently threw a bunch of money into it. More here

Since linux in all its many flavors is not windows they have to go with a shotgun style approach/recipe to support everything linux as a guest. That mostly works, but its not considered clean nor is it technically the “Debian way” that both Ubuntu and Debian users are generally better off succumbing to.