shutting down the computer puts me to the login screen

recently installed suse 11 with xfce.

when i click on the quit button, the system just performs s regular logout and shows me the login screen, so i have to do su -> then shutdown or login as root and shut down.

how can i enable to everyone to shutdown the computer?
in yast i couldnt find any related option.
i thought i could mess around with sudo is yast but i first thought i should find some other option