A trouble string that cause an error

in 2.6RC, string like "<div[^>]*>[^<>]*(((?'Open'<div[^>]*>)[^<>]*)+((?'-Open'</div>)[^<>]*)+)*(?(Open)(?!))</div>" will be translate into "<p><span class="regex">]*>[^<>]*(((?'Open']*>)[^<>]*)+((?'-Open'</span><p> </p></p><div> </div><p>)[^<>]*)+)*(?(Open)(?!))</p><div> </div>"

that's wrong, why?