valgrind invalid read error

Running nautilus from precise under valgrind and ubuntuone-client-gnome 2.99.90, I got those errors in the log:

==10300== Invalid read of size 4
==10300== at 0x4A590BE: g_type_check_instance_cast (gtype.c:3994)
==10300== by 0x7F76A32: foreach_weak_unref (file-watcher.c:37)
==10300== by 0x4AAEC17: g_hash_table_foreach (ghash.c:1524)
==10300== by 0x7F76D2D: file_watcher_finalize (file-watcher.c:48)
==10300== by 0x4A395B7: g_object_unref (gobject.c:3018)
==10300== by 0x7F79735: ubuntuone_nautilus_finalize (ubuntuone-nautilus.c:166)
==10300== by 0x4A395B7: g_object_unref (gobject.c:3018)
==10300== by 0x812657E: free_module_objects (nautilus-module.c:236)
==10300== by 0x4D504D2: (below main) (libc-start.c:226)
==10300== Address 0x1304d7f8 is 0 bytes inside a block of size 216 free'd
==10300== at 0x402B06C: free (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==10300== by 0x4AC4EBA: standard_free (gmem.c:98)
==10300== by 0x4AC502F: g_free (gmem.c:252)
==10300== by 0x4AD948A: g_slice_free1 (gslice.c:1111)
==10300== by 0x4A57A81: g_type_free_instance (gtype.c:1937)
==10300== by 0x4A3962A: g_object_unref (gobject.c:3031)
==10300== by 0x80FCB57: nautilus_file_unref (nautilus-file.c:864)
==10300== by 0x4ABBE57: g_list_foreach (glist.c:900)
==10300== by 0x810569C: nautilus_file_list_unref (nautilus-file.c:7520)
==10300== by 0x80E1C36: nautilus_directory_stop_monitoring_file_list (nautilus-directory-async.c:2237)
==10300== by 0x80E02A1: nautilus_directory_async_state_changed (nautilus-directory-async.c:2247)
==10300== by 0x80E50D8: nautilus_directory_monitor_remove_internal (nautilus-directory-async.c:1144)
==10300== by 0x81336AF: vfs_file_monitor_remove (nautilus-vfs-directory.c:110)
==10300== by 0x80E8D58: nautilus_directory_file_monitor_remove (nautilus-directory.c:1542)
==10300== by 0x80DA9E0: merged_monitor_destroy (nautilus-desktop-directory.c:264)
==10300== by 0x4AAD5B7: g_hash_table_remove_node (ghash.c:484)
==10300== by 0x4AADD39: g_hash_table_remove_internal (ghash.c:1274)
==10300== by 0x80DAC8C: desktop_monitor_remove (nautilus-desktop-directory.c:347)
==10300== by 0x80E8D58: nautilus_directory_file_monitor_remove (nautilus-directory.c:1542)
==10300== by 0x80B0BA9: disconnect_model_handlers (nautilus-view.c:9153)

==10300== by 0x80BF961: nautilus_view_destroy (nautilus-view.c:2612)
==10300== by 0x4A3638B: g_cclosure_marshal_VOID__VOID (gmarshal.c:85)
==10300== by 0x4A3349C: g_type_class_meta_marshal (gclosure.c:970)
==10300== by 0x4A34571: g_closure_invoke (gclosure.c:777)
==10300== by 0x4A46EF2: signal_emit_unlocked_R (gsignal.c:3663)
==10300== by 0x4A4F6CF: g_signal_emit_valist (gsignal.c:3295)
==10300== by 0x4A4F8D2: g_signal_emit (gsignal.c:3352)
==10300== by 0x43A397F: gtk_widget_dispose (gtkwidget.c:10338)
==10300== by 0x4A3AB36: g_object_run_dispose (gobject.c:1061)
==10300== by 0x4396750: gtk_widget_destroy (gtkwidget.c:3943)
==10300== by 0x80CB55D: nautilus_window_slot_dispose (nautilus-window-slot.c:217)
==10300== by 0x4A394D1: g_object_unref (gobject.c:2981)
==10300== by 0x4A39661: g_value_object_free_value (gobject.c:3301)
==10300== by 0x4A5BC45: g_value_unset (gvalue.c:276)
==10300== by 0x4A4F6F5: g_signal_emit_valist (gsignal.c:3324)
==10300== by 0x4A4F8D2: g_signal_emit (gsignal.c:3352)
==10300== by 0x418F335: gtk_container_remove (gtkcontainer.c:1538)
==10300== by 0x4269862: gtk_notebook_remove_page (gtknotebook.c:7019)
==10300== by 0x80C9C87: nautilus_window_pane_close_slot (nautilus-window-pane.c:1091)