We could not write /var/www/sandbox.drupal6.civicrm.org/public/sites/sandbox.drupal6.civicrm.org/files/civicrm/upload/.htaccess. Have you moved your site directory or server?<p>Please fix the setting by running the <a href="http://sandbox.drupal6.civicrm.org/civicrm/admin/setting/updateConfigBackend?reset=1">update config script</a>