Anti-Splog plugin breaks some custom post types

I'm at a loss here. The below code snippet creates a Portfolio on my site whenever a relevant portfolio item is added. The code has always worked fine prior to enabling the Anti-Splog plugin.

I've tested multiple combinations, enabled/disabled all plugins, played with .htaccess, etc. and whenever I enable the Anti-Splog plugin, I get a 'page not found' error for my portfolios. Disabling the plugin doesn't fix it immediately; I have to disable all plugins to get it working again. I can re-enable all, plugins except Anti-Splog and it works fine. When I re-enable Anti-Splog, it stops working again.

Here's the code that creates the custom post type in my theme's functions.php:

/** Create portfolio custom post type */
add_action( 'init', 'portfolio_post_type' );
function portfolio_post_type() {
	register_post_type( 'portfolio',
		array(
			'labels' => array(
				'name' => __( 'Portfolio', 'website' ),
				'singular_name' => __( 'Website Portfolio', 'website' ),
			),
			'exclude_from_search' => true,
			'has_archive' => true,
			'hierarchical' => true,
			'menu_icon' => get_stylesheet_directory_uri() . '/images/icons/portfolio.png',
			'public' => true,
			'rewrite' => array( 'slug' => 'portfolio' ),
			'supports' => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'trackbacks', 'custom-fields', 'comments', 'revisions', 'page-attributes' ),
		)
	);
}

/** Change the number of portfolio items to be displayed */
add_action( 'pre_get_posts', 'website_portfolio_items' );
function website_portfolio_items( $query ) {

	if( $query->is_main_query() && !is_admin() && is_post_type_archive( 'portfolio' ) ) {
		$query->set( 'posts_per_page', '12' );
	}

}

I've done some digging through the Anti-Splog plugin and can't find what the conflict might be. The odd thing is that when I pulled these two functions out of the theme's functions.php and dropped them into a custom plugin it works fine...no issues.

Can I get a dev's help troubleshooting this? Is it a bug? Am I missing something simple? Thanks.

Notes: I'm using the Genesis theme framework and the latest version of multisite.