Error when submitting comment

I receive this error when trying to add a comment to a user profile.
Also, many other features do not load (or take forever, and does not refresh the page such as adding friend etc).

"Undefined property: Clake\Userextended\Models\UserExtended::$created_at" on line 374 of /var/www/html/mysite/plugins/rainlab/user/models/User.php
