Cisco VPNC 3000 - Windows PPTP VPN Client?

I'm trying to set up a cisco VPN Concentrator 3000 using a Windows
PPTP VPN Client. I believe that everything is set up correctly on the
Concentrator, and the client but I'm not able to make it work. It does
connect to the server then attempt to go thru authentication but stops
there. After waiting about 20 secs I get an "error 619 The specified
port is not connected" - there is no additional info. On the VPNC's
log's i can see the PPTP tunnel get established then end with a
message "Tunnel to peer <IP_Address> closed, reason: None (No
additional info)"

I've actually done a capture on the communication between my client
and the concentrator and everything looks normal until my client sends
the first GRE (PPP) Packet - looks like "PPP LCP Configuration
Request" It sends one of these packets about every 4 seconds but
doesnt recieve a reply from the server, until about 20-30 secs later
and the the server sends a regular PPTP Clear-Request packet?

When I try to the the cisco client it's not working either but that
actually seems unreleated..

Any idea's out there?

THX
Matthew