If I try to run a program with GUI (e.g. Nautilus) as root, I'm just getting the following output:
gksu nautilus
Fontconfig warning: "/etc/fonts/conf.d/50-user.conf", line 9: reading configurations from ~/.fonts.conf is deprecated.
Invalid MIT-MAGIC-COOKIE-1 keyCould not parse arguments: Anzeige kann nicht geöffnet werden: