Misunderstanding: The error is expected because 10.0.0.126 doesn't exist on the network. ("xhost +" was done before, also x was started without any xauth-magic that could add additional trouble.) The unexpected and interesting part of the game is that you don't see this error on the 770. Mind you, even if xhost/xauth/... setting were all correct, the IP-address doesnt exist, there's no way to open a display on the remote machine. Still, there's no error and the application runs locally.