in punbb 1.2.4
replace line 41 of index.php
// Print the categories and forums
$result = $db->query('SELECT c.id AS cid, c.cat_name, f.id AS fid, f.forum_name, f.forum_desc, f.redirect_url, f.moderators, f.num_topics, f.num_posts, f.last_post, f.last_post_id, f.last_poster FROM '.$db->prefix.'categories AS c INNER JOIN '.$db->prefix.'forums AS f ON c.id=f.cat_id LEFT JOIN '.$db->prefix.'forum_perms AS fp ON (fp.forum_id=f.id AND fp.group_id='.$pun_user['g_id'].') WHERE fp.read_forum IS NULL OR fp.read_forum=1 ORDER BY c.disp_position, c.id, f.disp_position', true) or error('Unable to fetch category/forum list', __FILE__, __LINE__, $db->error());
with
// Print the categories and forums
$result = $db->query('
SELECT c.id AS cid, c.cat_name, f.id AS fid,
f.forum_name, f.forum_desc, f.redirect_url,
f.moderators, f.num_topics, f.num_posts,
f.last_post, f.last_post_id, f.last_poster,
t.subject
FROM '.$db->prefix.'categories AS c
INNER JOIN '.$db->prefix.'forums AS f ON c.id=f.cat_id
INNER JOIN '.$db->prefix.'posts AS p ON p.id=f.last_post_id
INNER JOIN '.$db->prefix.'topics AS t ON t.id=p.topic_id
LEFT JOIN forum_perms AS fp ON (fp.forum_id=f.id AND fp.group_id='.$pun_user['g_id'].')
WHERE fp.read_forum IS NULL OR fp.read_forum=1
ORDER BY c.disp_position, c.id, f.disp_position
', true) or error('Unable to fetch category/forum list', __FILE__, __LINE__, $db->error());
replace line 109 index.php
// If there is a last_post/last_poster.
if ($cur_forum['last_post'] != '')
$last_post = '<a href="viewtopic.php?pid='.$cur_forum['last_post_id'].'#p'.$cur_forum['last_post_id'].'">'.format_time($cur_forum['last_post']).'</a> <span class="byuser">'.$lang_common['by'].' '.pun_htmlspecialchars($cur_forum['last_poster']).'</span>';
with
// If there is a last_post/last_poster.
if ($cur_forum['last_post'] != '')
$last_post = format_time($cur_forum['last_post']).' '.$lang_common['by'].' '.pun_htmlspecialchars($cur_forum['last_poster']).'<span class="byuser"> in <a href="viewtopic.php?pid='.$cur_forum['last_post_id'].'#p'.$cur_forum['last_post_id'].'">'.pun_htmlspecialchars($cur_forum['subject']).'</a></span>';