Comment 16 for bug 207693

https://bugs.edge.launchpad.net/ubuntu/+source/libwnck/+bug/199380 is the same bug and contains a valgrind showing the issue :

==27419== Invalid read of size 4
==27419== at 0x44B87D1: gtk_tooltip_start_delay (gtktooltip.c:1015)
==27419== by 0x44B93DF: _gtk_tooltip_handle_event (gtktooltip.c:1298)
==27419== by 0x43DBCF9: gtk_main_do_event (gtkmain.c:1608)
==27419== by 0x464FA99: gdk_event_dispatch (gdkevents-x11.c:2351)
==27419== by 0x4858D15: g_main_context_dispatch (gmain.c:2003)
==27419== by 0x485C0D2: g_main_context_iterate (gmain.c:2636)
==27419== by 0x485C68D: g_main_context_iteration (gmain.c:2699)
==27419== by 0x751BDF3: processEvents (gconf.c:1886)
==27419== by 0x757B13D: ccsProcessEvents (main.c:1729)
==27419== by 0x7544549: wnck_pager_query_tooltip (in /usr/lib/libwnck-1.so.22.3.6)
==27419== by 0x43E09A3: _gtk_marshal_BOOLEAN__INT_INT_BOOLEAN_OBJECT (gtkmarshalers.c:835)
==27419== by 0x47EE078: g_type_class_meta_marshal (gclosure.c:567)
==27419== by 0x47EF82E: g_closure_invoke (gclosure.c:490)
==27419== by 0x4804119: signal_emit_unlocked_R (gsignal.c:2478)
==27419== by 0x4805946: g_signal_emit_valist (gsignal.c:2209)
==27419== by 0x4805EDF: g_signal_emit_by_name (gsignal.c:2267)
==27419== by 0x44B9275: gtk_tooltip_run_requery (gtktooltip.c:747)
==27419== by 0x44B9485: _gtk_tooltip_handle_event (gtktooltip.c:1256)
==27419== by 0x43DBCF9: gtk_main_do_event (gtkmain.c:1608)
==27419== by 0x464FA99: gdk_event_dispatch (gdkevents-x11.c:2351)
==27419== by 0x4858D15: g_main_context_dispatch (gmain.c:2003)
==27419== by 0x485C0D2: g_main_context_iterate (gmain.c:2636)
==27419== by 0x485C68D: g_main_context_iteration (gmain.c:2699)
==27419== by 0x751BDF3: processEvents (gconf.c:1886)
==27419== by 0x757B13D: ccsProcessEvents (main.c:1729)
==27419== by 0x7544549: wnck_pager_query_tooltip (in /usr/lib/libwnck-1.so.22.3.6)
==27419== by 0x43E09A3: _gtk_marshal_BOOLEAN__INT_INT_BOOLEAN_OBJECT (gtkmarshalers.c:835)
==27419== by 0x47EE078: g_type_class_meta_marshal (gclosure.c:567)
==27419== by 0x47EF82E: g_closure_invoke (gclosure.c:490)
==27419== by 0x4804119: signal_emit_unlocked_R (gsignal.c:2478)
==27419== by 0x4805946: g_signal_emit_valist (gsignal.c:2209)
==27419== by 0x4805EDF: g_signal_emit_by_name (gsignal.c:2267)
==27419== by 0x44B9275: gtk_tooltip_run_requery (gtktooltip.c:747)
==27419== by 0x44B9485: _gtk_tooltip_handle_event (gtktooltip.c:1256)
==27419== by 0x43DBCF9: gtk_main_do_event (gtkmain.c:1608)
==27419== by 0x464FA99: gdk_event_dispatch (gdkevents-x11.c:2351)
==27419== by 0x4858D15: g_main_context_dispatch (gmain.c:2003)
==27419== by 0x485C0D2: g_main_context_iterate (gmain.c:2636)
==27419== by 0x485C68D: g_main_context_iteration (gmain.c:2699)
==27419== by 0x751BDF3: processEvents (gconf.c:1886)
==27419== Address 0x48 is not stack'd, malloc'd or (recently) free'd