Index: xfce4-session/xfsm-fadeout.c
===================================================================
--- xfce4-session/xfsm-fadeout.c	(revision 22110)
+++ xfce4-session/xfsm-fadeout.c	(working copy)
@@ -145,7 +145,21 @@
   g_free (fadeout);
 }
 
+void
+xfsm_fadeout_refresh (XfsmFadeout *fadeout)
+{
+  FoScreen *screen;
+  GList    *lp;
 
+  for (lp = fadeout->screens; lp != NULL; lp = lp->next)
+    {
+      screen = lp->data;
+
+      gdk_window_clear (screen->window);
+    }
+}
+
+
 static void
 xfsm_fadeout_drawable_mono (XfsmFadeout *fadeout,
                             GdkDrawable *drawable)
Index: xfce4-session/xfsm-fadeout.h
===================================================================
--- xfce4-session/xfsm-fadeout.h	(revision 22110)
+++ xfce4-session/xfsm-fadeout.h	(working copy)
@@ -30,6 +30,7 @@
 typedef struct _XfsmFadeout XfsmFadeout;
 
 XfsmFadeout *xfsm_fadeout_new     (GdkDisplay  *display);
+void         xfsm_fadeout_refresh (XfsmFadeout *fadeout);
 void         xfsm_fadeout_destroy (XfsmFadeout *fadeout);
 
 G_END_DECLS;
Index: xfce4-session/shutdown.c
===================================================================
--- xfce4-session/shutdown.c	(revision 22110)
+++ xfce4-session/shutdown.c	(working copy)
@@ -168,6 +168,7 @@
   XfceKiosk *kiosk;
   gboolean kiosk_can_shutdown;
   XfceRc *rc;
+  GList *lp;
 #ifdef SESSION_SCREENSHOTS
   GdkRectangle screenshot_area;
   GdkWindow *root;
@@ -433,6 +434,19 @@
   if (!accessibility)
     xfsm_window_grab_input (GTK_WINDOW (dialog));
 
+  /* 
+   * Note (Olivier):
+   * Some compositors, such as the one in xfwm4, unredirect
+   * fullscreen override-redirect windows, and that causes
+   * a unmap/map event which clears the fadeout window.
+   * The following portion of code aimed at processing 
+   * all pending events and clears the window to force
+   * a redraw.
+   */
+  while(gtk_events_pending()) 
+    gtk_main_iteration();
+  xfsm_fadeout_refresh (fadeout);
+
   /* run the logout dialog */
   result = gtk_dialog_run (GTK_DIALOG(dialog));