"Registry object is not an object in" with "fetch_session_complete"

[Skyrider]

Now, as you are all aware.. I'm still learning a few things here and there. I recently got the idea to include some code into the fetch_session_complete hook for the users session. However, whenever I attempt to use any of my pre-existing code such as:

$userdata->set('usergroupid', xx);

I've been getting the error message "Registry object is not an object in" -> "class_dm.php"

I've already included quite a few files, including the global.php file but clearly I'm doing something wrong here. Any pinpointers are welcome. I do really hope I can even alter the usergroup within the fetch_session_complete hook.

Maybe I forgot to add more includes?

require_once(DIR . '/includes/functions.php');
require_once(DIR . '/includes/class_core.php');
require_once('global.php');