Problem PXE booting from VM

[dac]

Hi all, I am trying to use FOG to image machines on a LAN, but first I am practising on my own machine with VMs. I have followed the steps on "http://192.168.90.208/fog/management/index.php?node=about&sub=pxemenu" to install the FOG server. I have installed Oracle VM Virtual Box and I have loaded an Ubuntu Server virtual disk to the VM. I have set the system to boot from the network and I have set the network to use a bridged adaptor, however when I start up the VM it goes straight the Ubuntu login, seemingly missing the PXE boot from my FOG server altogether.

The connections between the FOG server and VM are there as I can successfully PING from the FOG client to the VM and from the VM to the FOG client

Any help would be greatly appreciated.