Well, THAT made me think...so i investigated a bit. Zweihander-sector is using a port (3544), that is used by an internal IPv6 <-> IPv4 Wrapper/Tunnel AND unfortunatly by a worm trying to break into systems by using this port. Most likely, that many desktop-firewalls have a standard rule (default rule set) blocking this port.   Just an idea, but i changed the emulator server now to not use this port anymore, so we will see if Zweihander is fine with th