I have had lots of trouble getting my host VM, Hyper-V and Virtual server hosts to see the guests. Thining it was my tardoness I had tried other apps without success. Finally I tried the new Virtual Server 2005 R2 SP1....got the same damn issue!
Did some hunting arund and found this that started me on the right track...
What I did to get it working:
Install loopback adapter on host and left to DHCP.
Created new virtual network and pointed it at my Physical adapter.
Verfiy firewall on virtual host off -> all OK ???
I give up - loopback adapater did not come into it at all!!!
There's bound to be a reason....