Windows – How well do Macs work with Windows Home Server

Another alternative would be KeepVault. They seem to have better pricing.

How do you have your network setup in the Virtual Machine?

It sounds like you might have it setup using NAT. In this situation, if your host machine(Mac) has a non-routable(private) IP address such as 192.168.x.x, you will not be able to reach the host from within the virtual machine. The reason you cannot reach the host from the guest is that you are essentially setting up 2 separate private networks. Your Mac computer is on one (192.168.x.x) and your VM on another (perhaps 10.x.x.x) and you essentially have a router between them. Since routers will not route private IPs, the two networks can never communicate with each directly.

If you want your host and guest machines to be able to communicate, you will probably want to setup your VirtualBox network adapter to be attached to the "Bridged Adapter." This will share your internet connection with the virtual machine and allow your guest machine to talk to the host. In this situation you are essentially adding your VM as an additional node to the local network your Mac is already on.