Gtk-WARNING **: cannot open display
I am using SUSE 9.1 and am having a peculiar problem that I don't understand.
If I log into KDE as user1 and run firefox (or any gui app) at the command line, no problem. If I "su - root", set DISPLAY=ipaddress_of_machine:0.0, I get a long wait and eventually an error
"Gtk-WARNING **: cannot open display"
The same happens when I log into KDE as root (run 'xhost +' just to be sure) and "su - user1", set DISPLAY=ipaddress_of_machine:0.0
If I don't set the DISPLAY variable, I get the error instantaneously, as one would expect. I don't know what else to look for and the long delay before the error makes me thing there may be something else wrong or something is not set up properly.