MM Forms edit data error php fix

MM Forms Pro 2.1.0 Saves form data but if you edit that data this error message appears upon save: Warning: Cannot modify header information - headers already sent by (output started at /home/cultured/public_html/wp-content/plugins/mm-forms/includes/[login to view URL]) in /home/cultured/public_html/wp-content/plugins/mm-forms/includes/[login to view URL] on line 23 The data edit is not saved. Installed on Wordpress 3.1.3 Need this fixed.