Thumbs are shown smaller than I want

Hello there
I’m having some troubles with the thumb function in my wordpress theme. I’m using the following code in my index.php file:

<?php /* if the post has a WP 2.9+ Thumbnail */
							if ( (function_exists('has_post_thumbnail')) && (has_post_thumbnail()) ) : ?>
							<div class="post-thumb post-lead">

								<a title="<?php printf(__('Permanent Link to %s', 'framework'), get_the_title()); ?>" href="<?php the_permalink(); ?>"><?php the_post_thumbnail(); ?><?php add_theme_support( 'post-thumbnails' ); /* post thumbnail settings configured in functions.php */ ?></a>

and this one in function.php:

if ( function_exists( 'add_theme_support' ) ) { // Added in 2.9
	add_theme_support( 'post-thumbnails' );
	set_post_thumbnail_size( 570, 300, true ); // Normal post thumbnails
	add_image_size( 'medium', 570, 300, true ); // Medium size
	add_image_size( 'archive-thumb', 570, 300, true ); // Post thumbs
	add_image_size( 'gallery-thumb', 570, 300, true ); // Gallery thumbs
}

Also I adjusted the sizes in the wordpress backend settings (I don’t konw if this is necessary, but I just wanted to make it everywhere the same). But that won’t work. The thumbs are always too small and are not cutted (they keep the dimensions). Here is the link. Maybe you could help. I see in Firebug, that somehow the image-size is indicated with 200×133 px. Thank you very much!