title: Error after login to Magento on core/Mage/Admin/Model/User.php on line 437
body: <p>None of out programmers has changed anything to the code, but out of nothing now, when a user tries to login on the backend, we have this error: </p>
  
  <blockquote>
    <p>Fatal error: Call to a member function children() on a non-object in
    /home/r1tech/public_html/app/code/core/Mage/Admin/Model/User.php on
    line 437</p>
  </blockquote>
  
  <p>Any ideas why this is happening?</p>