Cannot intiate a Video or Voice Conversation, Please Help!!

Okay, this is the deal: Both machines have XP Pro SP2, firewalls have been
disabled, Router/Hub is a Westel VersaLink 327W on both machines, Upnp is
enabled on both routers, firewalls on routers are disabled, custom ports have
been added specified by Microsoft 6901 etc, both versions of messenger is
4.7. We get connecting to name of computer then it error's out and says:

he network or computer you are trying to reach is experiencing a problem.
Please try again later.

I am at my wits end. I have been working on this problem forever. I also
took my laptop over to her house connected it to her network wirelessly and
we could video and voice conference no problem. What am I doing wrong???
Please Help me.

Rebecca