Patch 1

Other forum members already signalled that code is missing in 
[my-site]\components\com_content\views\category\tmpl\blog.php
see http://forum.joomla.org/viewtopic.php?f=624&t=723468
The solution proposed also picks up the show_no_articles parameter and has been tested on a couple of live 2.5.9 sites, including a multi-lingual one.