title: Drupal doesn't save any changes in admin settings
body: <p>I have a strange problem in drupal. When I'm trying to change <code>_any_</code> setting in the drupal admin (caching under performance, temp-directory under file-system, default filter under filters, etc) I get the message that the changes were saved successful, but the values don't change.</p>
  
  <p>I don't know where to start debugging since this is such a widespread problem. I've checked rights of all files/folder and the database connection. Seems fine.</p>
  
  <p>Anyone experienced such a problem before?</p>
  
  <p>edit: There isn't a single error entry in the drupal log file.</p>
  
  <p>edit 2: I just deactivated every single contrib module. Still I can't make any changes to (for example) the caching mode.</p>