Index: panel/panel-app.c
===================================================================
--- panel/panel-app.c	(revision 28345)
+++ panel/panel-app.c	(working copy)
@@ -428,7 +428,11 @@
     {
         monitor = g_ptr_array_index (panel_app.monitor_list, i);
 
-        if (monitor->screen == screen)
+        /* 
+         * With xrandr 1.2, monitors can be added/removed, so need 
+         * to double check the number of monitors (bug #3620)...
+         */
+        if ((monitor->screen == screen) && (monitor->num < gdk_screen_get_n_monitors (screen)))
         {
             gdk_screen_get_monitor_geometry (screen, monitor->num,
                                              &(monitor->geometry));