Retrieve modification date of a talk page
This is expected behaviour since talk namespaces are by default not enabled to hold semantic annotations. Besides, your setup is a bit scary. You should really upgrade not just for the sake of security but also for all the nice features introduces since
Many thanks for your quick reply and the pointer! It's good to know this setting because we want to introduce custom namespaces and move some existing pages to namespaced ones.
You are right regarding the scary part. An upgrade to more current versions of MW and SMW is already planned for the near future ;-)