Custom shortcode stopped working

I added a functions.php file to my theme directory containing the following code to create a shortcode tag, [site-link]:

<?
function link_shortcode($attr, $content = NULL) { 

    extract( shortcode_atts( array(
          'name' => '',
          'link' => '',
          ), $atts ) );

         global $post;
         $link = get_post_meta($post->ID,'site-link', true);
         $name = get_post_meta($post->ID,'site-name', true);

          $output = '<span class="source-link">[from&nbsp;<a href="'.$link.'" title="Read the rest of this story">'.$name.'</a>]</span>';

          return $output;
}
?>

It *was* working beautifully (you can see the output here: http://www.rchseaglesnest.org — the bottom of the page, the “Around the Web” section.), but all of a sudden stopped. Now it just outputs the raw tag, [site-link]

My understanding of what I was doing was tenuous at best when I started. Now I’m not really sure how to troubleshoot — does anybody know factors that might make such a thing “stop working”?

Thanks for any ideas!
Jeff.