Dear all: I found a workaround to this problem in https://lists.dyne.org/lurker/message/20151017.174509.c6a14ccc.en.html (Debian is not Gnome' forum):
install xserver-xorg-legacy and add "needs_root_rights=yes" to /etc/X11/Xwrapper.config It worked for me, though I wonder how much time will this '-legacy' package will be functional. Thank you girls! Zhana
