Black screen fix (due to socket problems) should be fixed with a program called Winsock fix, I've had two people I know with this issue try it with sucess! Fluke? maybe but it's worth a shot!
It's easy to use all you have to do it download the program here: http://www.softpedia.com/get/Tweak/Network-Tweak/WinSockFix.shtml
run the program, after it dings done reboot your PC. Load GPGnet test hosting/joining with someone. (As it should work afterwards)