Today I got problem with showEffect in my project, when I added my component via PopUpManager.addPopUp I notice that showEffect doesn’t run.
To get it working you need add creationComplete handled inside component and dispatch FlexEvent.SHOW event in created handler.
happy coding 
July 19th, 2009 at 3:20 am
Thank you! I ran into this issue and found that your tip fixed it! On a side note, I kept playing with it and noticed that if you use the creationCompleteEffect instead of the showEffect, then sending the SHOW event is not necessary. The other ‘gotcha’ I found was that I needed to declare the effect in the scope of the parent and not in the pop-up component.