title: CodeIgniter 2.2.0 HMAC mismatch error
body: <p>UPDATE: Even after downloading the "fixed" 2.2.0, update log files are still filling up with:</p>
  
  <blockquote>
    <p>Session: HMAC mismatch. The session cookie data did not match what was
    expected.</p>
  </blockquote>
  
  <p>After upgrading from CodeIgniter 2.1.3 to 2.2.0 I am getting the error:</p>
  
  <blockquote>
    <p>Session: HMAC mismatch. The session cookie data did not match what was
    expected.</p>
  </blockquote>
  
  <p>The Mcrypt extension is enabled. If I set $config['sess_encrypt_cookie'] = FALSE; (not an option for production) there is no error. Any help greatly appreciated.</p>