Hi,
           FYI I have ported fedora 15 for my target board (x86 based arch.)
           when i switch any user to gnome-fallback mode,i cant relogin once i do switch-user.GDM login screen freezes and i have to restart my system.
{            also,switch user works fine if i use  instead of gnome-fallback            }

LOGS:
              1.)    :0-greeter.log
                       _IceTransmkdir: ERROR: euid != 0,directory /tmp/.ICE-unix will not be created.

(gnome-settings-daemon:2761): Gtk-WARNING **: gtk_window_set_wmclass: shouldn't set wmclass after window is realized!

** (process:2797): DEBUG: Greeter session pid=2797 display=:0 xauthority=/var/run/gdm/auth-for-gdm-cBntFM/database
Failed to play sound: File or data not found

(gnome-power-backlight-helper:2840): PowerManager-WARNING **: failed to find any devices: Error opening directory '/sys/class/backlight': No such file or directory
gdm-simple-greeter[2797]: Gtk-WARNING: gtkwidget.c:6778: widget not within a GtkWindow
gdm-simple-greeter[2797]: Gtk-WARNING: gtk_widget_size_allocate(): attempt to allocate widget with width -47 and height -47
Window manager warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x1600007 (Login Wind)
Window manager warning: meta_window_activate called by a pager with a 0 timestamp; the pager needs to be fixed.


             2.)  /home/user_name/.xsession-erros
IceTransmkdir: Owner of /tmp/.ICE-unix should be set to root
gnome-keyring-daemon: error getting process capabilities, aborting
gnome-keyring-daemon: error getting process capabilities, aborting
gnome-keyring-daemon: error getting process capabilities, aborting
gnome-keyring-daemon: error getting process capabilities, aborting
Applet requires SELinux be enabled to run.

** (deja-dup-monitor:3576): WARNING **: Network.vala:40: Error calling StartServiceByName for org.freedesktop.NetworkManager: GDBus.Error:org.freedesktop.DBus.Error.Spawn.ChildExited: Launch helper exited with unknown return code 1

Failed to play sound: File or data not found
** Message: applet now removed from the notification area

** (nm-applet:3583): WARNING **: get_all_cb: couldn't retrieve system settings properties: (25) Launch helper exited with unknown return code 1.

** (nm-applet:3583): WARNING **: fetch_connections_done: error fetching connections: (25) Launch helper exited with unknown return code 1.

** (nm-applet:3583): WARNING **: Failed to register as an agent: (25) Launch helper exited with unknown return code 1


Regards
Lokesh