IE9.js fails the :last-child test when dev console open in IE8

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Open the [http://ie7-js.googlecode.com/svn/test/last-child.html :last-chile 
test page]
2. Verify that the last element is yellow
3. Open the console (F12)
4. Reload the page
5. Last child's yellow background dissapears
6. Close console
7. Reload page
8. Last child's background is yellow again

What is the expected output? What do you see instead?
The last child element should stay yellow regardless of dev console visibility.

What version of the product are you using? On what operating system?
ie9.js 2.1beta4 (SVN, as per usage instructions).

Please provide any additional information below.
I'm using IE8 in IE8 standards mode. This script doesn't seem to correctly 
apply last-child rules in my HTML5 app, too. Though I noticed this odd 
behaviour when verifying the tests to see if it matched my use case.

Original issue reported on code.google.com by krof.drakula on 30 Jul 2010 at 6:51

[GoogleCodeExporter]

Actually, testing out :last-of-type on the test pages exhibits the same 
behavior.

Try the same on http://ie7-js.googlecode.com/svn/test/of-type.html

Original comment by krof.drakula on 30 Jul 2010 at 6:58