post_category not being assigned to posts in wp_posts table

When I save a post in wp-admin it doesn’t write the post_category number to the post in the wp_posts table. When I view the posts in wp-admin -> Manage, the category name is displayed as if it were properly assigned to that category.

I had some issues with my categories and had to change their IDs by hand. I think this messed everything up.

Does anyone have any ideas how to fix this?