Script With Document.write Inside Iframe Hangs First Time, Works Second Time (in IE)?

I have put together a script which does this:

1. Make ajax request (via getHTTPObject(), no libraries is used)

2. Create an iframe with script, src is "blank.html".

3. use iframe.document.write() to execute scripts (inkluding document.write based scripts) in the iframe.

4. call parent window's document to clone the iframe content.

5. Append the content clone to parent body.

Works like a charm in all browsers but IE, where every version - including IE9 beta - hangs on iframeWindow.document.close() with empty cache, leaving the window/tab unresponsible. When I force quit, restart and load the page again (now in cache) it works.What I've tried already:

* Googled.

* called the ajax request callback manually with string instead of request.responseText - it works even with empty cache here.Removed document.close() - resulting in scripts in iframe not executing at all (again, only with empty cache, cached pages works fine).

* Tested to make the ajax request synchronous - no difference.

Console.log trace:

Code:
append() begin
unlimited-scroll.js:160 install() begin
unlimited-scroll.js:194 iframe begin[code].....