Upgraded to Fusion 4 and now I can't access web server on my host Mac

I am running OSX 10.6.8, and I am hosting a VM running windows XP, using NAT Networking. I have a web server running on the mac which I need to access from the hosted VM. I used to be able to just use the IP address of the gateway in the VM to get to the web server but this doesn't seem to work anymore. If I put in the external IP address of the mac this seems to work, but I don't have a static IP so this is a pain to update every time.

Any help would be appreciated!

Thanks