Here's a simple HTML which does not work. It should display Portal demo in iframe. Works well in Firefox and Chrome. Does not work in IE8.
It was working with previous public release (4.0.7). Does not work with ExtJS 4.1.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head></head><body><iframe frameborder="0" height="2000px" id="itarget" name="itarget" scrolling="auto" src="http://dev.sencha.com/deploy/ext-4.1.0-gpl/examples/portal/portal.html" title="Content" width="100%"></iframe></body></html>
*** EDIT 6/21/12
I recreated this problem using 4.1.1 RC2. This bug occurs only for iframes, works fine in a regular frame.
Can you retest your example with 4.1.1 GA?
We use iframes in IE in the Page Analyzer, so the problem is likely specific to certain configuration of iframe and parent. The bug report descriptions were updated to include what we believed was the root of the problem: different domains.