Version 6.3 and firewalls

[Dave]

We recently installed a software firewall called Black Ice. If the firewall
is on when we click on an item to put it in the shopping cart the connection
times out and we receive an error saying the page cannot be displayed.
Turning the firewall off allows the shopping cart to work.

I can find nothing helpful in either the documentation or knowledgebase.
Does anyone know what ports or settings would allow the firewall to function
as well as the shopping cart?

Thanks