PPTP VPN Passthrough using NAT

Hi

I'm using Windows 2000 as a guest on ubuntu Dapper. I set up networking using NAT. Everything works fine, except I cannot connect t a PPTP vpn from the guest. When I try that, I get a hit on my hosts firewall, for GRE protocol.

My computer is behind a router that also does NAT, and it passes PPTP to the host just fine, so I'm sure the problem is with vmware.

What can I do?

Haggai