This message is immediately followed by the Xlib: Client is not authorized to connect to Server message. These messages indicate that an X windows application tried to run on the X server specified inside double quotes, which did not allow the request. The 0.0 represents the display device, which is usually the console. If no servername appears, the superuser probably tried to run an X application on the current machine in an X session that was owned by somebody else.
To allow this client to connect to the X server, run xhost(1) +clientname on the X server system. Only the owner of the current X session (who is not necessarily the superuser) is allowed to run the xhost(1) command. If somebody else is running X windows on the server, ask them to log out and then start your own X session on that server; remote X connections are usually allowed for the same user ID.