shawn@eggplantstudios.ca on "function convert_to_screen() no longer exists in template.php?"

I solved it by adding

require_once(ABSPATH . 'wp-admin/includes/template.php' );

to my plugin file which creates the class; Then in my class constructor:

parent::__construct( array(
            'singular'  => 'interval',     //singular name of the listed records
            'plural'    => 'intervals',    //plural name of the listed records
            'ajax'      => false,        //does this table support ajax?
            'screen'      => 'interval-list'        //hook suffix
        ) );

Adding the 'screen' => 'interval-list' fixed the Hook Suffix error.