VPN Issue

okay, clients outside network get an Error 721 when trying to connect oto Windows 2000 Adv Server. Server has Remote Access installed, with VPN enabled. Two NIC cards…Linksys router in front of it. Port forwarding for 1723 and 47 on to the IP address of one of the static nic cards…and pptp passthrough enabled. We can connect internally just fine, of course. Ideas?? Need fixed oh so fast.