in the past, i've always been able to use su to start an X application, for example, say i'm loogged on as slinky and i do an "su root" and then "firefox", it would start up firefox as root. Now when i do that, it gives an error:
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified
(firefox-bin:4905): Gtk-WARNING **: cannot open display:
i can start firefox fine, if i log into X as root. why does this happen? how can i change it back?