Clicking and/or typing in editing area throws a javascript error - Versions 4.1.2 & 4.2.1

Very basic HTML:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
    <title>My Page</title>
    <script type="text/javascript" src="http://code.jquery.com/jquery-1.7.2.min.js"></script>
    <script
        type="text/javascript"
        src="/assets/js/ckeditor_4.2.1_full/ckeditor.js"></script>
    <script type="text/javascript">
        $(function(){
            CKEDITOR.replace('my_text');
        });
    </script>
</head>
<body>
    <form method="post">
        <textarea name="my_text">dfagasdf sdf<br /><br />dasf asdf</textarea>
    </form>
</body>
</html>

Frequently when clicking and/or typing into the editing area, the following javascript errors are thrown in IE9, sometimes causing the editor to stop working:

Mon, 09/23/2013 - 20:15

reinmar

Joined: 24/08/2012

Posts: 631

I replied on Stack Overflow -

I replied on Stack Overflow - http://stackoverflow.com/questions/18963101/why-is-ckeditor-throwing-a-javascript-error-when-i-click-or-type-in-the-text-are

Piotrek (Reinmar) Koszuliński
CKEditor JavaScript Developer
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