http://forum.1cpublishing.eu/showthread.php?t=22038
Or join a server thats already up... I disagree with your analysis that its steam... Has anything changed on yours or your friends machine? IP, Routers, Firewalls, UAC, antispyware and antivirusware?
Do you both have the same patch version? 1.05, 1.06, 1.07 or 1.08?
