How can i make VISTA networking the same as XP?

I have an application, and it works fine on XP. So I installed it on Vista,
and the program runs fine, but when it connects to the server, it says "can
not locate server". I verified all the settings are correct. You can choose
"Run as" other OS, but that does nothing for you as far as the network is
concerned.

Is there anyway to emulate XP's networking on Vista? How could the program
work, but not the networking. I tried removing IPV6, and just using IPV4. I
also tried the obvious, removing the firewall.

I suspect this has something to do with RPC, or some security protocol. It
would be REALLY helpful if someone can guide me with this. The app is for a
Toshiba CS Phone server software, and our vendor is playing hardball with us
to get the Vista updates.