The problem is that the code is already as high up as it can go in Single.php. All that stuff between the content and the page nav is being auto generated and inserted into the end of the post.
<div class="entry-utility">
<?php twentyten_posted_in(); ?>
<?php edit_post_link( __( 'Edit', 'twentyten' ), '<span class="edit-link">', '</span>' ); ?>
</div><!-- .entry-utility -->
</div><!-- #post-## -->
<div id="nav-below" class="navigation">
<div class="nav-previous"><?php previous_post_link( '%link', '<span class="meta-nav">' . _x( '←', 'Previous post link', 'twentyten' ) . '</span> %title' ); ?></div>
<div class="nav-next"><?php next_post_link( '%link', '%title <span class="meta-nav">' . _x( '→', 'Next post link', 'twentyten' ) . '</span>' ); ?></div>
</div><!-- #nav-below -->