Custom post type is showing custom home page, not archive page

I have a custom post type set up (two, actually) that are not displaying properly. I am hoping that it is the same issue with both post types.

Here is my code for one of the post types (portfolio). The second is quite similar.

?php
add_action('init', 'ccd_portfolio');

function ccd_portfolio() {

    $labels = array(
        'name' = _x('Portfolio', 'post type general name'),
        'singular_name' = _x('Project', 'post type singular name'),
        'add_new' = _x('Add New', 'ccd_portfolio item'),
        'add_new_item' = __('Add New Project'),
        'edit_item' = __('Edit Project'),
        'new_item' = __('New Project'),
        'view_item' = __('View Project'),
        'search_items' = __('Search Projects'),
        'not_found' =  __('Nothing found'),
        'not_found_in_trash' = __('Nothing found in Trash'),
        'parent_item_colon' = ''
    );

    $args = array(
        'labels' = $labels,
        'public' = true,
        'publicly_queryable' = true,
        'show_ui' = true,
        'query_var' = true,
        'menu_icon' = get_stylesheet_directory_uri() . '/images/icons/plugins/portfolio.png',
        'capability_type' = 'post',
        'hierarchical' = false,
        'menu_position' = null,
        'supports' = array('title', 'editor', 'excerpt', 'author'),
        'can_export' = true,
        'show_in_menu' = true,
        'has_archive' = true,
        'rewrite' = array('slug' = 'work')
      ); 

    register_post_type( 'portfolio' , $args );
    flush_rewrite_rules();
}

add_action("admin_init", "ccdport_admin_init");

function ccdport_admin_init(){
  add_meta_box("mb_ccdport_details", "Project Details", "ccdport_details", "portfolio", "normal", "high");
  add_meta_box("mb_ccdport_client", "Client", "ccdport_client", "portfolio", "side", "high");
}

add_action( 'admin_enqueue_scripts', 'ccdport_add_datepicker' );
function ccdport_add_datepicker(){
  wp_enqueue_script( 'jquery-ui-datepicker' );
  wp_enqueue_style('jquery-datepicker-style', 'http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.2/themes/smoothness/jquery-ui.css');
}
function ccdport_details(){
  global $post;
  $custom = get_post_custom($post-ID);
  $preview_url = $custom['preview_url'][0];
  $start_date = $custom['start_date'][0];
  $end_date = $custom['end_date'][0];
?
  plabelPreview URL: stronghttp:///strong
    input type="text" size="35" name="preview_url" value="?php echo $preview_url; ?" //p
  plabelStart date:/label
    input id="startDate" type="text" size="15" class="DatePicker" name="start_date" value="?php echo $start_date; ?" / nbsp;
    labelEnd date:/label
    input id="endDate" type="text" size="15" class="DatePicker" name="end_date" value="?php echo $end_date; ?" //p
    script
      jQuery(document).ready(function() {
        jQuery('input.DatePicker').datepicker({
          dateFormat : 'dd-mm-yyyy'
        });
      });
    /script
?php
}

function ccdport_client(){
  global $post;
  $custom = get_post_custom($post-ID);
  $client = $custom['project_client'][0];
  $name = $custom['client_name'][0];
  $args = array(
    'post_type' = 'clients',
    'posts_per_page' = -1,
    'orderby' = 'name',
    'order' = 'ASC'
  );
?
  plabelClient name/label/p
  input type="text" name="client_name" value="?php echo $name; ?" /
  plabelOrganisation/label/p
?php
  $query = new WP_Query( $args );
  if ( $query-have_posts() ){
    echo 'select name="project_client"';
    while ( $query-have_posts() ){
      $query-the_post();
      $slug = $post-post_name;
      echo 'option value="'.$slug.'" '.selected($slug, $client).''.get_the_title().' ('.$slug.')/option';
    }
    echo '/select';
  }
  else { echo 'pThere are currently no clients registered/p'; }
}

add_action('save_post', 'ccdport_save_details');

function ccdport_save_details(){
  global $post;

  update_post_meta($post-ID, "client_name", $_POST["client_name"]);
  update_post_meta($post-ID, "project_client", $_POST["project_client"]);
  update_post_meta($post-ID, "portfolio", $_POST["portfolio"]);
  update_post_meta($post-ID, "preview_url", $_POST["preview_url"]);
}
?

Each post type is included in a separate file, and called to functions.php with an include command. These are showing up in the admin area perfectly, posts are being saved perfectly, etc. However, the theme files (archive-portfolio.php and single-portfolio.php) are not loading. Instead, my custom home page is being displayed.

I don't know what the issue would be. I have flushed the rewrite rules with each post type, and removing that does nothing either. I have only recently started with custom post types, so any assistance would be extremely helpful. I have had a look through the other answers and they don't seem to be helpful in my situation. I've tried resaving my permalinks, to no avail. I've tried changing 'has_archive' = true to 'has_archive' = 'portfolio', nothing. Is there something I have missed? More than likely something glaringly obvious?