non root user cannot open applications

Hello ,
I had peform login (to an x window  session ) as root.
I had added a user (let's call him nonRoot)  ,to a RH9 machine.
Now, I perform su  nonRoot.

When I try to open z application (or peform xhost +localhost) I get the 
following error:
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

xhost:  unable to open display ":0.0"

what should I do ?
regards,
sting

_________________________________________________________________
STOP MORE SPAM with the new MSN 8 and get 2 months FREE* 
http://join.msn.com/?page=features/junkmail


_______________________________________________
xfree86-list mailing list
[email protected]
https://www.redhat.com/mailman/listinfo/xfree86-list
IRC: #xfree86 on irc.redhat.com