Hi Nick,
I changed the configuration.php: literally to
public $error_reporting = 'maximum';
On the administrator/index.php I don't get any error reports. Still just a blank page.
Now that you mentioned a rogue plugin, I suddenly remember installing the component extplorer 2.1.3 just before the issue of the blanc back-end page occured.
When I tried to run extplorer the first time i did not get any resluts.
I did remove the files of this component in both the components directory from the Joomla root and the adminstrator. I searched for any similar issue reports on the site
extplorer.net/ but did not find anything.
But on the other hand I also did change user rights just before the issue occured. As you explained this was a bug in J2.5.1. Should I clean up something regarding to the session in de database ?
Thanks for your patience; this issue surely is a challenge I guess.
Kind regards
Howard