Error in Membership Plugin

Hi,

I just installed the Membership Plugin for the first time, and when I set the membership level for the first user, i received the following error:

Warning: Missing argument 2 for wpdb::prepare(), called in /home/ime/public_html/staff/wp-content/plugins/membership/membershipincludes/classes/class.membership.php on line 447 and defined in /home/ime/public_html/staff/wp-includes/wp-db.php on line 990