messege that the conversation is ended.

[Mandi]

I'm developing some software based on Messenger technology. I learned from
on of the exports how to run MSN Messenger and Microsoft Messenger on the
same PC and communicate between them. I use voice conversations. I added the
needed protocol in the router - Upnp. Problem is that whenever the PC is
connected through a USB modem, all works fine. Sometimes (not always)When
its connected with a router, with NAT it doesn't work and I get a message
that the conversation is ended.

Can someone advise how to solve the problem?

Thanks

Mandi