Valgrind reports this:

==670== 32 bytes in 1 blocks are definitely lost in loss record 9815 of 15025
==670==    at 0x1B9057A8: realloc (vg_replace_malloc.c:378)
==670==    by 0x1C66867D: g_realloc (gmem.c:170)
==670==    by 0x1C67B24B: g_string_maybe_expand (gstring.c:239)
==670==    by 0x1C67B6BA: g_string_insert_len (gstring.c:479)
==670==    by 0x1C67B959: g_string_append (gstring.c:505)
==670==    by 0x1BCDA19B: gnome_vfs_uri_to_string (gnome-vfs-uri.c:1207)
==670==    by 0x1D76C5D3: gtk_file_system_gnome_vfs_get_parent
(gtkfilesystemgnomevfs.c:1206)
==670==    by 0x1C176C8C: gtk_file_system_get_parent (gtkfilesystem.c:531)
==670==    by 0x1C163C73: update_label_and_image (gtkfilechooserbutton.c:1825)
==670==    by 0x1C16447A: dialog_selection_changed_cb (gtkfilechooserbutton.c:2067)
==670==    by 0x1C5C0EFC: g_cclosure_marshal_VOID__VOID (gmarshal.c:77)
==670==    by 0x1C5B60EB: g_closure_invoke (gclosure.c:437)
==670==    by 0x1C5C4272: signal_emit_unlocked_R (gsignal.c:2488)
==670==    by 0x1C5C5636: g_signal_emit_valist (gsignal.c:2247)
==670==    by 0x1C5C87DC: g_signal_emit_by_name (gsignal.c:2315)
==670==    by 0x1C16F7B1: delegate_selection_changed (gtkfilechooserutils.c:321)
==670==    by 0x1C5C0EFC: g_cclosure_marshal_VOID__VOID (gmarshal.c:77)
==670==    by 0x1C5B60EB: g_closure_invoke (gclosure.c:437)
==670==    by 0x1C5C4272: signal_emit_unlocked_R (gsignal.c:2488)
==670==    by 0x1C5C5636: g_signal_emit_valist (gsignal.c:2247)
==670==    by 0x1C5C87DC: g_signal_emit_by_name (gsignal.c:2315)
==670==    by 0x1C16F7B1: delegate_selection_changed (gtkfilechooserutils.c:321)
==670==    by 0x1C5C0EFC: g_cclosure_marshal_VOID__VOID (gmarshal.c:77)
==670==    by 0x1C5B60EB: g_closure_invoke (gclosure.c:437)
==670==    by 0x1C5C4272: signal_emit_unlocked_R (gsignal.c:2488)
==670==    by 0x1C5C5636: g_signal_emit_valist (gsignal.c:2247)

Attaching a patch that might fix it.