PopUpManager is unable to pop up the component if visible / includeInLayout of any of the children is false

Steps to reproduce:
1. I have created a simple application to demonstrate the bug. Hit the URL: http://208.109.28.58:9080/FlexIssuePopUp/FlexIssuePopUp.html (view source enabled)
2. Click on 'pop up flags' button
2. In the popped up control, click on any of the 3 check boxes
3. Click on 'submit' button
4. Click on 'pop up flags' button again

Actual Results:
The parent window gets disabled but the control with check boxes does not pop up.

Expected Results:
The control with check boxes is expected to pop up

Workaround (if any):