I dont think this is anything to do with your firewall... The windows firewall only blocks incoming connections as far as I am aware, or if it does block outgoing connections they will certainly not be any connections that would cause you to drop off the network. Why do you need to use group policy settings anyway? The Group Policy objects just allow you to change things that you can change in the windows firewall control panel applet (Start -> Run -> Firewall.cpl). But like I said, I dont think its the firewall that is doing it.