RSS Feed "This feed contains code errors" in IE8

An RSS feed that I have in my site used to work but now won’t display in IE and displays an error page saying “This feed contains code errors” and I’m totally unsure as to why as it works fine in other browsers. Can anyone scan through this code for me and tell me what the problem is:-

[code=php]


<?php

$siteurl = “http://www.mysite.co.uk/”;

require_once(‘connectionfile.php’);
mysql_select_db($database, $myconnection);

$today = date(‘Y-m-d’);

$query = “(SELECT * FROM teachers WHERE is_ranked = 1 AND type <> 3 AND expiration_date > ‘$today’) UNION (SELECT * FROM teachers WHERE type <> 3 AND expiration_date > ‘$today’)”;
$result = mysql_query($query);

while ($line = mysql_fetch_assoc($result))
{
$return[] = $line;
}

$now = date(“D, d M Y H:i:s T”);

$output = “<?xml version=”1.0″?>
<rss version=”2.0″>
<channel>
<title>teachers</title>
<link>”.$siteurl.”RSS-Feed.php</link>
<description>RSS</description>
<language>en-us</language>
<pubDate>$now</pubDate>
“;

foreach ($return as $line)
{

$teacherclass_id = $line[‘class_id’];
$result_getteacherclass = mysql_query(“SELECT * FROM classs WHERE class_id = $teacherclass_id”);
$row_getteacherclass = mysql_fetch_assoc($result_getteacherclass);

$output .= “<item><title>”.htmlentities($line[‘teacher_name’]).”</title>
<link>”.htmlentities($siteurl.$row_getteacherclass[‘class_url_name’]).”.co.uk</link>

<description>”.htmlentities(strip_tags($line[‘description’])).”</description>
<pubDate>”.htmlentities($line[‘join_date’]).”</pubDate>
</item>”;
}
$output .= “</channel></rss>”;
header(“Content-Type: application/rss+xml”);
echo $output;
?>

[/code]

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