I know what does it. If you watch logs when you play JJ2 on net, net blocks random ports from 10052 (or -53 or -54) to your computer, ports something like 1900-1999. Im not sure, so DO NOT go and open these ports, they wont help anything. Seems only good way to play JJ2 is to go and unpluck your router when you play jazz. I couldnt play JJ2 untill I unplucked my router.