[kh99]

In external.php around line 409, try replacing the entire "if type is js" block with this:

if ($vbulletin->GPC['type'] == 'JS')
{ // javascript output
	$output = "
	function thread(threadid, title, poster, threaddate, threadtime, preview)
	{
		this.threadid = threadid;
		this.title = title;
		this.poster = poster;
		this.threaddate = threaddate;
		this.threadtime = threadtime;
		this.preview = preview;
	}
	";
	$output .= "var threads = new Array(" . sizeof ($threadcache) . ");\r\n";
	if (!empty($threadcache))
	{
		require_once(DIR . '/includes/class_bbcode_alt.php');
		foreach ($threadcache AS $threadnum => $thread)
		{
			$thread['title'] = addslashes_js(htmlspecialchars_uni($thread['prefix_plain']) . $thread['title']);
			$thread['poster'] = addslashes_js($thread['postusername']);
			$plaintext_parser = new vB_BbCodeParser_PlainText($vbulletin, fetch_tag_list($vbulletin->options['bburl'] . '/'));
			$preview = $plaintext_parser->parse($thread['message'], $thread['forumid']);
			unset($plaintext_parser);
                        if (strlen($preview) > 23) $preview = substr($preview, 0, 23) . "...";
                        $preview = addslashes_js($preview);
			$output .= "\tthreads[$threadnum] = new thread($thread[threadid], '$thread[title]', '$thread[poster]', '" . addslashes_js(vbdate($vbulletin->options['dateformat'], $thread['dateline'])) . "', '" . addslashes_js(vbdate($vbulletin->options['timeformat'], $thread['dateline'])) . "', '" .
$preview . "');\r\n";
		}
	}
}

Then you should be able to use thread[x].preview in your js code. You might want to comment out the existing if block so you can easily bring it back if needed.

BTW, I put the length limiting code in the php so you don't need to check in your js. Or if you'd rather have it in the js you can of course remove that line from the php.