cant start X apps using su or sudo
 

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: i can start firefox fine, if i log into X as root. why does this happen? how can i change it back?

For security reasons, your X server only allows connections from the user that started it. If you do "xhost +localhost", that will allow connections from all users on the local system. See "man xhost" for more details.

it didnt work. i did xhost +localhost and it said "localhost being added to access control list", but then i tried to su and start firefox and it gave me that error.

Try xhost +<your host name> -- if that doesn't work, make sure that the $DISPLAY environment vaqriable is set in your su shell.