Esse código era da página "page.php". Troquei de ficheiro ao fazer a pesquisa e não me apercebi...
Fica aqui o código da index:
<?php get_header(); ?>
<div class="main_table">
<div class="main_table_row">
<div class="left_1"><img src="<?php bloginfo('stylesheet_directory'); ?>/images/spacer.gif" alt="" align="top" style="width:1px; height:1px"/></div>
<div class="main_cent">
<div class="co_name_bg">
<div class="co_name">
</div>
</div>
<div class="head_bg">
<div class="table2">
<div class="table_row">
<div class="left2">
<?php $count = 1; ?><?php if (have_posts()) : ?>
<?php while (have_posts()) : the_post();
$thumb = get_post_meta($post->ID, 'imagem', $single = true);
?>
<table width="589" border="0" cellspacing="0" cellpadding="0" style="margin-top:0px;">
<tr>
<td valign="top">
<!-- BEGIN left -->
<div class="left_box">
<div class="content_left_top">
</div>
<div class="content_left_bg">
<?php // if there's a thumbnail
if($thumb !== '') { ?>
<p>
<img src="<?php echo $thumb; ?>" width="180" height="130" />
</p>
<?php } // end if statement
// if there's not a thumbnail
else { echo ''; } ?>
<div class="content_left">
<h2><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>
<div class="meta1">
</div>
<div style="margin:5px 0 10px 0; border-top: 1px dashed #fff;"></div>
<?php
$content = get_the_excerpt('',FALSE,'');
$content = apply_filters('the_content', $content);
$content = str_replace(']]>', ']]>', $content);
echo substr($content,0,290);
?>…
</div>
</div>
<div class="content_left_bottom">
</div>
<!-- end post -->
</div>
<!-- END left -->
</td>
<td valign="top">
</td>
</tr>
</table>
<?php if ($count == 1) : ?>
<div align="center" style="margin-bottom:8px;">
<?php include (TEMPLATEPATH . "/post_ad.php"); ?>
</div>
<?php endif; $count++; ?>
<?php endwhile; ?>
<?php else : ?>
<h2>ERRO - Nenhum artigo encontrado</h2>
<?php endif; ?>
<div class="wp-pagenavi">
<?php if (function_exists('wp_pagenavi')) : ?>
<?php wp_pagenavi(); ?>
<?php else : ?>
<?php next_posts_link('« Página Anterior'); ?>
<?php previous_posts_link('Página Seguinte »'); ?>
<?php endif; ?>
</div>
<div class="comment">
</div>
</div>
<div class="right2">
</div>
</div>
</div>
</div>
</div>
<div class="main_left">
<?php include (TEMPLATEPATH . "/sidebar.php"); ?>
</div>
<div class="right_1"><img src="<?php bloginfo('stylesheet_directory'); ?>/images/spacer.gif" alt="" align="top" style="width:1px; height:1px"/></div>
</div>
</div>
<?php get_footer(); ?>
</div>
</div></div>
</body>
</html>