diff -Naur xfce4-systemload-plugin-0.4.2.old/panel-plugin/systemload.c xfce4-systemload-plugin-0.4.2/panel-plugin/systemload.c
--- xfce4-systemload-plugin-0.4.2.old/panel-plugin/systemload.c	2009-10-09 13:13:35.510019151 +0200
+++ xfce4-systemload-plugin-0.4.2/panel-plugin/systemload.c	2009-10-09 14:40:00.683234643 +0200
@@ -933,9 +933,18 @@
 
     update_monitors (global);
 
+	/* reduce the default tooltip timeout to be smaller than the update interval otherwise
+	 * we won't see tooltips on GTK 2.16 or newer */
+	GtkSettings *settings;
+	settings = gtk_settings_get_default();
+	if (g_object_class_find_property(G_OBJECT_GET_CLASS(settings), "gtk-tooltip-timeout"))
+		g_object_set(settings, "gtk-tooltip-timeout",
+					 UPDATE_TIMEOUT - 10, NULL);
+
     global->timeout_id = 
         g_timeout_add(UPDATE_TIMEOUT, (GSourceFunc)update_monitors, global);
     
+
     g_signal_connect (plugin, "free-data", G_CALLBACK (monitor_free), global);
 
     g_signal_connect (plugin, "save", G_CALLBACK (monitor_write_config),