Losing TCP access to hosted OS when VPN client is runing on host

With no VPN client active, from my host (MAC OSX 10.4.10), I can access a web server running on my hosted virtual windows XP machine, using the default IP (http://10.211.55.3).

If I load a VPN (Cisco VPN Client 4.9.00) on my host (OSX), I can access the VPN from both the host OSX and the virtual windows. This works fine.

The problem: From my host OSX, I can no longer access the web server running in my virtual machine using the above IP address.

Any idea why that is?

--
Claude