title: error after joomla upgrade 2.5.3 to 2.5.6
body: <p>I have a fatal error after upgrading joomla from 2.5.3 to 2.5.6 and couldnt find any solutions on all the forums. After failed to upgrade joomla via the admin backend, I downloaded and installed joomla upgrade 2.5.6 using the install extensions panel. And it said that installation was successfull.</p>
  
  <p>Afterwards loging in to the admin panel, everythings is empty, only the "view site" and "logout" buttons to the top right are visible.</p>
  
  <p>On the frontend following error is shown.</p>
  
  <p>Warning: Invalid argument supplied for foreach() in /homepages/44/d33570217/htdocs/joomla/libraries/joomla/application/menu.php on line 90</p>
  
  <p>Warning: Invalid argument supplied for foreach() in /homepages/44/d33570217/htdocs/joomla/includes/application.php on line 449</p>
  
  <p>Warning: Creating default object from empty value in /homepages/44/d33570217/htdocs/joomla/includes/application.php on line 471</p>
  
  <p>Fatal error: Call to a member function get() on a non-object in /homepages/44/d33570217/htdocs/joomla/templates/beez_20/error.php on line 10</p>
  
  <p>the upgrade must have overwritten some files and I cannot localize the problem. It is not a template problem, I have tried switching it in the database. Configuration.php is also ok, all values are identical to before the upgrade.</p>
  
  <p>Can someone help me to find out the problem? Thanks</p>