Creating a simple widget

I followed the new wordpress widget API and did this simple widget:

class CategoryWidget extends WP_Widget{

    function CategoryWidget(){
    $widget_ops = array('classname' => 'categories', 'description' => __( "Theme-default category block") );
    $this->WP_Widget('categories', __('My Categories',), $widget_ops);
    }

    function widget($args, $instance){
      extract($args);
      $title = apply_filters('widget_title', empty($instance['title']) ? '' : $instance['title']);
	  $orderby = empty( $instance['orderby'] ) ? 'name' : $instance['orderby'];
      $showcount = isset($instance['showcount']) ? $instance['showcount'] : false;

      echo $before_widget;

      if ( $title ) echo $before_title . $title . $after_title;

      // content......

      echo $after_widget;
  }

    function update($new_instance, $old_instance){
      $instance = $old_instance;
      $instance['title'] = strip_tags(stripslashes($new_instance['title']));

	  if ( in_array( $new_instance['orderby'], array( 'name', 'ID', 'slug','count' ) ) ) {
			$instance['orderby'] = $new_instance['orderby'];
		} else {
			$instance['orderby'] = 'name';
		}

   	  if ( isset($new_instance['showcount']) ) $instance['showcount'] = 1;

    return $instance;
  }

    function form($instance){
      // defaults
      $instance = wp_parse_args( (array) $instance, array('orderby' => 'name', 'title'=>'Categories', 'showcount' => false) );

      $title = htmlspecialchars($instance['title']);

      echo '<p><label for="' . $this->get_field_name('title') . '">' . __('Title:',) . ' <br /><input class="widefat" id="' . $this->get_field_id('title') . '" name="' . $this->get_field_name('title') . '" type="text" value="' . $title . '" /></label></p>';

     ?>

     <p>
	    <label for="<?php echo $this->get_field_id('orderby'); ?>"><?php _e( 'Sort categories by:', ); ?></label>
		<select name="<?php echo $this->get_field_name('orderby'); ?>" id="<?php echo $this->get_field_id('orderby'); ?>" class="widefat">
		 <option value="name"<?php selected( $instance['orderby'], 'name' ); ?>><?php _e('By name (alphabetically)',); ?></option>
		 <option value="ID"<?php selected( $instance['orderby'], 'ID' ); ?>><?php _e('By category ID',); ?></option>
     	 <option value="slug"<?php selected( $instance['orderby'], 'slug' ); ?>><?php _e('By category slug',); ?></option>
		 <option value="count"<?php selected( $instance['orderby'], 'count' ); ?>><?php _e( 'By post count', ); ?></option>
		</select>
	 </p>

	 <label for="<?php echo $this->get_field_id('showcount'); ?>"><?php _e('Show Link showcount',); ?></label>
	 <input class="checkbox" type="checkbox" <?php checked($instance['showcount'], true) ?> id="<?php echo $this->get_field_id('showcount'); ?>" name="<?php echo $this->get_field_name('showcount'); ?>" />

     <?php

  }
}

function MyWidgetsInit(){
  register_widget('CategoryWidget');
}

add_action('widgets_init', 'MyWidgetsInit');

the problem is that I can’t update some of the widget options from the dashboard. I can only set the title. “sortby” and “showcount” fields don’t work, they just revert to the default value after I press save…

I checked the code over and over again, and see no reason why it shouldn’t work…

did I miss something?