custom post types and archive pages

Hey. I got a problem when using custom post types. I described it here before:

https://stackoverflow.com/questions/4951537/wordpress-custom-post-type-categories

I register this custom post type like this:

register_post_type("lifestream", array(
            'label' => 'Lifestream',
            'public' => true,
            'hierarchical' => true,
            'menu_position' => 5,
            'supports' => array('title','editor','author','thumbnail','comments','custom-fields'),
            'taxonomies' => array('category','post_tag'),
            'query_var' => true,
            'publicly_queryable' => true,
            'exclude_from_search' => false,
            'caller_get_posts' => 1

        ));
        register_taxonomy_for_object_type('category', 'lifestream');
        register_taxonomy_for_object_type('post_tag', 'lifestream');

In the theme (the loop template) I like to combine posts and my custom post type, for that I am using query_posts() with these parameters:

$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$args = array(
    'post_type' => array('post', 'lifestream'),
    'paged' => $paged,
    'cat' => $wp_query->get('cat'),
    'tag' => $wp_query->get('tag'),
    'year' => $wp_query->get('year'),
    'monthnum' => $wp_query->get('monthnum'),
    'post_status' => 'publish',
    'showposts' => 3
);
query_posts($args); 

# the loop
while ( have_posts() ) : the_post();
# markup
endwhile;

if($wp_query->max_num_pages > 1):
# next_posts_link / previous_posts_link
endif;

wp_reset_query();

This is working so far. But, I got problems with the category and tags pages. If I call the frontpage everything is fine and I can paginate through the pages getting the correct results.

And, if I call a paged URL, e.g. /category/mycat/page/2 a 404 is thrown. But there definitly should be posts. No matter if there are custom type posts or normale posts in the category. I suppose that my parameters for query_posts() aren′t correct, but don′t know …

Do you have any Idea what to do? Thanks a lot!