Sorry forgot to mention that :( -
You need to modify the portfolio options to support custom fields. To do this, open /theme_options/portfolio.php and find this code (around line 59):
$args = array(
'labels' => $labels,
'public' => true,
'show_ui' => true,
'capability_type' => 'post',
'hierarchical' => false,
'rewrite' => array('slug'=>$slugRule,'with_front'=>true),
'query_var' => true,
'show_in_nav_menus'=> false,
'menu_position' => 5,
'supports' => array('title','thumbnail','excerpt','editor','comments')
);
Change the supports to include custom fields like this:
$args = array(
'labels' => $labels,
'public' => true,
'show_ui' => true,
'capability_type' => 'post',
'hierarchical' => false,
'rewrite' => array('slug'=>$slugRule,'with_front'=>true),
'query_var' => true,
'show_in_nav_menus'=> false,
'menu_position' => 5,
'supports' => array('title','thumbnail','excerpt','editor','comments','custom-fields')
);