If you made the modifications to the layout.master file of your skin as described here it will work:
http://www.mojoportal.com/using-the-async-google-analytics-controls.aspx
demo.mojoportal.com is now using the async script as I have updated all the included skins to use it.
make sure you are editing the correct layout.master file, the site does not use the skins from /Data/skins, it uses them from /Data/Sites/1/skins
Hope it helps,
Joe