strange popup behaviour on iphone 4

strange popup behaviour on iphone 4

Hi all,
I created a web app using JQM 1.3.1.
All is almost fine.
I only have a problem: I have a popup menu on the footer that should ... popup!... once tapped. It only popups when I have NOT added the webapp to the iphone home. Once I add the web app to the iphone home the popup menu doesn't popup anymore.
Has someone seen something similar?

TIA

tony