Can't run Guarddog v2.6.0 in Gnome v2.30?

Hi.

A few days ago, I installed a new clean Debian stable since my old one 
from 2004 was badly shaped. I am still trying to configure it up like my 
old one from scratch. 

How do I run Guarddog v2.6.0 with root/sudo access in Gnome v2.3 since I 
don't like KDE v4.4.3 (currently installed too)? I can run Guarddog 
without problems if I use KDE and it even asks my root/sudo password.

I noticed running Guarddog as root/sudo in Terminal in Gnome shows:
# guarddog
No protocol specified
guarddog: cannot connect to X server :0.0

I have no problems running other KDE programs like kmail, kruler, etc. 
in Gnome though. 

FYI, I use Guarddog because it is easy to configure my iptables. ;)

Thank you in advance. :)

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