Installation error - "could not open display"

[Hexar]

When I install run the scalix 11 GA installer in my CentOS box, the following error shown

Scalix Installer - extracting archive, please wait...
Scalix Installer - starting version 11.0.0.653...
Scalix Installer - using Python 2.3.4 (/usr/bin/python).
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

Error: 'could not open display'.
Make sure your DISPLAY environment variable is set to the host and port of your running X server.
Scalix Installer - cleaning up...
Scalix Installer - done.

Any idea?

[ls-al]

You are probably installing with a ssh-session that is forwarding X11-packets and have no local X-Server running.

use the --cli switch for scalix-installer.