WordPress data base error

Every thing was fine. The only thing I have done over the last twenty four is upload a couple of themes and the one I was experimenting with was working fine. I then delteted it but nothing else, the only files I was playing with were theme files.

Not at the top of my blog no matter which theme I choose I have this.

WordPress database error: [You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘) ORDER BY post_date DESC LIMIT 0, 1’ at line 1]
SELECT SQL_CALC_FOUND_ROWS DISTINCT wp_posts.* FROM wp_posts LEFT JOIN wp_post2cat ON ( wp_posts.ID = wp_post2cat.post_id) WHERE 1=1 AND (post_type = ‘post’ AND (post_status = ‘publish’ OR post_status = ‘private’)) AND category_id NOT IN () ORDER BY post_date DESC LIMIT 0, 1″

I under stand what it says but have no idea as to why all of a sudden it happened and have no idea how to fix it.

Any thought?