result of compiz command then activating visual effects:
Starting gtk-window-decorator
(gtk-window-decorator:632): Gdk-WARNING **: GdkWindow 0x10003a4 unexpectedly destroyed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): Gdk-WARNING **: GdkWindow 0x100040d unexpectedly destroyed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): Gdk-WARNING **: GdkWindow 0x10002a3 unexpectedly destroyed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): Gdk-WARNING **: GdkWindow 0x10004f5 unexpectedly destroyed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): Gdk-WARNING **: GdkWindow 0x1000472 unexpectedly destroyed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): Gdk-WARNING **: GdkWindow 0x10000c1 unexpectedly destroyed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
(gtk-window-decorator:632): Gdk-WARNING **: GdkWindow 0x10000b5 unexpectedly destroyed
(gtk-window-decorator:632): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
Segmentation fault
Do you use the Compiz PPA?