NAT and VPN issue?

I am having a very strange issue with my Checkpoint VPN connection. My VM starts fine and can connect to the web fine and I can login to my corp network via Checkpoint. This is where it gets strange... I can open network folders from a Run box in XP, but I can't connect to our Exchange and Project Servers. Now the wierd part - if i release the IP address from the Ethernet adapter in XP, leave it as 0.0.0.0 I can connect to Exchange and Project with no issue. But, as expected, in a few minutes the VPN connection breaks with a "IP address has changed" error.

The VM was built by migrating from an existing Laptop that connected fine to corp network.

Configuration is as follows:

MAC OSX Leopard, AirPort, DHCP, Shared Internet Connection, NAT Adapter configured with DHCP and gets correct address

Parallels: Shared Network Connection, v3.0, Build 5626

XP: SP3, IP configured with DHCP

Thanks in advance for your help.