WordPress database error

I have just upgraded to 2.3 but when I try to publish or save a post I get this error:

WordPress database error: [Table 'wordp.wp_post2cat' doesn't exist]
SELECT cat_ID AS ID, MAX(post_modified) AS last_mod FROM <code>wp_posts</code> p LEFT JOIN <code>wp_post2cat</code> pc ON p.ID = pc.post_id LEFT JOIN <code>wp_categories</code> c ON pc.category_id = c.cat_ID WHERE post_status = 'publish' GROUP BY cat_ID

Warning: Cannot modify header information - headers already sent by (output started at /home/******/******/******/wp-includes/wp-db.php:160) in /home/******/******/******/wp-includes/pluggable.php on line 390