We're using a PIX 515 6.3(5) and we currently have our telecommuters using PPTP VPN connections to work from home or on the road. Users that are buying new machines with Windows Vista are having a hard time connecting to our network and I think it has something to do with the new IPv6 or other network settings. Whenever someone tries to connect to the firewall via VPN, they get a "Couldn't negotiate PPP parameters with remote host" message.
Is 6.3(5) compatible with IPv6? Do I need to add anything to our PIX config to get VPN connectivity working again with Vista?