Windows 7 64 bit connection problem

[visimp]

I have installed uVNC 1.1.9.x86 server on a Windows 7 64 bit computer and set the port to 4899
I can connect within the building using the local ip address:4899
Outside the building I can connect with a Windows XP machine using the wan ip address:4899 whcih shows I have opened the port in the router to the corresponding computer on the network.
However, when I attempt to connect from outside the building using two different Windows 7 computers, it fails to connect. The user at the server computer says the uVNC pops up a little message that says it cannot connect (back) to my Wan IP address.
I do not get the login window at all, just the error message from the viewer... cannot connect to server.... but it looks like it is the server that cannot connect back to me.
My Windows firewall is off. My Antivirus is off. I even tried with my lacal router firewall off. Still the same issue.

Any suggestions.....

[Bonji]

At first glance I would say you have a routing problem between the two computers. Does a traceroute on each computer match up between them?

Can you try any other service between the two computers in each direction?