I create a new user ab, so that no local config could have effect. I login as user ab, then, in a gnome terminal, I issue su - Password: xterm& and to my amazement, the xterm started with no errors. I cannot decide if this is a feature or bug. Thx Mate --- Mate Wierdl | Dept. of Math. Sciences | University of Memphis
It's a feature of pam_xauth; it passes X cookies along with su. See 'man pam_xauth' for more details.