diff -Naur xfce4-panel-4.8.1/plugins/tasklist/tasklist-widget.c xfce4-panel-4.8.1-modified/plugins/tasklist/tasklist-widget.c
--- xfce4-panel-4.8.1/plugins/tasklist/tasklist-widget.c	2011-01-30 17:28:20.000000000 +0100
+++ xfce4-panel-4.8.1-modified/plugins/tasklist/tasklist-widget.c	2011-02-08 15:40:17.307000002 +0100
@@ -1376,6 +1376,9 @@
       G_CALLBACK (xfce_tasklist_window_removed), tasklist);
   g_signal_connect (G_OBJECT (tasklist->screen), "viewports-changed",
       G_CALLBACK (xfce_tasklist_viewports_changed), tasklist);
+
+  /* MODIFICATION Pim Vullers: the screen changed (it was just added) */
+  xfce_tasklist_gdk_screen_changed (tasklist->gdk_screen, tasklist);
 }