While trying to find the problem on an old Joomla 2.5.11 website that had suddenly stopped working correctly, I found The Joomla Forum Post Assistant, shortened to (FPA), a nice and simple tool that helps one to detect possible problems on Joomla installations.
It's quite easy to use, just grab the latest version and uploaded it to your website, call it from the browser and that's it. Don't forget to remove it after you're done with it.
./M6