Wordpress als CMS: Kategorie-Seiten nicht sichtbar!

<?php // Tutors United Archive ('Aktuelle Veranstaltungen')  ?>
<?php get_header(); ?>
    <div id="content">
        <!-- Primary content: Stuff that goes in the primary content column (by default, the left column) -->
        <div id="primarycontainer">
            <div id="primarycontent">
                <div id="contentarea"><!-- Primary content area start -->


    <?php if (have_posts()) : ?>
            <?php $post = $posts[0]; // Hack. Set $post so that the_date() works. ?>
    <h3><?php echo single_cat_title(); ?></h3>
    
    <?php if (is_category()) { ?>
        <h2 class="pagetitle">Aktuelle Veranstaltungen</h2>
    <?php } elseif (function_exists('is_tag')&& is_tag()) { ?>
        <h2 class="pagetitle">Archiv f&uuml;r das Tag '<?php single_tag_title(); ?>'</h2>
    <?php } elseif (is_day()) { ?>
        <h2 class="pagetitle">Tagesarchiv f&uuml;r den <?php the_time('j. F Y'); ?></h2>
    <?php } elseif (is_month()) { ?>
        <h2 class="pagetitle">Monatsarchiv f&uuml;r <?php the_time('F Y'); ?></h2>
    <?php } elseif (is_year()) { ?>
        <h2 class="pagetitle">Jahresarchiv f&uuml;r <?php the_time('Y'); ?></h2>
    <?php } elseif (is_search()) { ?>
        <h2 class="pagetitle">Suchergebnisse</h2>
    <?php } elseif (is_author()) { ?>
        <h2 class="pagetitle">Autoren Archiv</h2>
    <?php } elseif (isset($_GET['paged']) && !empty($_GET['paged'])) { ?>
        <h2 class="pagetitle">Blog Archiv</h2>
    <?php } ?>
    
        <?php while (have_posts()) : the_post(); ?>


            <div class="post" id="post-<?php the_ID(); ?>">
                        <h4><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>"><?php the_title(); ?></a></h4>
                        <div class="contentarea">
                            <p class="details"><span class="user">Tutor: <?php the_author_posts_link() ?></span> <span class="date"><?php the_time('j. F Y') ?></span></p>
                            <?php the_content(); ?>
                                <p class="post-tags">
                                <?php if (function_exists('the_tags')) the_tags('Tags: ', ', ', '<br/>'); ?>
                                </p>
                            <ul class="controls">
                                <li class="more"><?php edit_post_link('Bearbeiten'); ?></li>                
                                <li class="comments"><?php comments_popup_link('Kommentare oder Anregungen? Frag den Tutor!', '1 Kommentar', '% Kommentare'); ?></li>                                    
                            </ul>
                        </div><!-- close contentarea -->
            </div><!-- close post -->




            </div>


        <?php endwhile; ?>


        <p align="center"><?php posts_nav_link(' - ','« Vorherige Eintr&auml;ge','N&auml;chste Eintr&auml;ge »') ?></p>
        
    <?php else : ?>
        <h2 class="center">Nichts gefunden.</h2>
    <?php endif; ?>
</div><!-- primarycontent end -->
        </div><!-- primarycontainer end -->
    </div><!--content end -->
<?php get_sidebar(); ?>
<?php get_footer();?>