Well last time i had network problems with WinPE in a virtual machine it was as a result of not having enough RAM allocated, remember it really wants at least 512MB. This time thought it took a little while to find the answer, and then I had to use Google's cache of a web page as the blog it pointed me to was down!  Anyhow Jason Huitt has a simple explanation - you need to add a Legacy Network addaptor under Add Hardware in the VMs Settings page.