ReflectionMedia

This should do the trick.

<?php
$args = array( 'numberposts' => 1, 'orderby' => 'rand', 'category' =>21 );
$rand_posts = get_posts( $args );
foreach( $rand_posts as $post ) : ?>
<a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>
<?php endforeach; ?>

try replacing the plus sign with a minus 🙂

Yes, I also get this problem.

But if a retry a couple dozen of times, it eventually works, I think maybe some servers are overworked… I dunno…

Gabriel