Updates in version 1.2:
Compatible with WordPress 3
Why it wasn’t working with WP3
WordPress had introduced Post Types in WP2.9. The default post types are post, page, attachment, revision, and nav-menu-item. WordPress had no restriction on applying taxonomies (category and tag) on any post type but had given the option to select for “post” post type only.
In WP3, the post type needs to be registered with taxonomy to be able to attached to it. The “page” post type is not registered with Category taxonomy so the plugin wasn’t able to save categories for pages in database.
What have been changed to make it compatible with WP3
I have used register_taxonomy_for_object_type function to enable “page” post type for Categories.