Random posts not working — followed it to the letter from Codex

Hi, I’m having an issue pulling a random testimonial post in my theme — I’ve tried this exactly as the codex says and no luck. Anyone see something I’m doing wrong? BTW, this is on an older install, 3.1 — not sure if that makes a difference.

<div id="quote-box">
     <?php $da_featured = new WP_Query( array ( 'orderby' => 'rand', 'posts_per_page' => '1', cat => '7' ) ); ?>
     <?php while ( $da_featured->have_posts() ) : $da_featured->the_post(); ?>
          <p>
	      <?php the_content(); ?>
          </p>
	  <em>
               -<?php the_title(); ?>
          </em>
     <?php endwhile; ?>
</div>