“Unknown Column in Field List” ????

Hello, when I edit/modify a page and hit save or save and continue editing I receive this error. Anyone have any idea what to do. It looks like it is giving me instructions, but I can’t be sure where to enter the code.

WordPress database error: [Unknown column 'none' in 'field list']
INSERT INTO wp_post2cat (post_id, category_id) VALUES (2, none)

Warning: Cannot modify header information - headers already sent by (output started at /home/themedit/public_html/wp-includes/wp-db.php:121) in /home/themedit/public_html/wp-includes/pluggable.php on line 275