Well, when I'm on the popup site, and click Jukebox, another popups DOES NOT come up above the original popup. It just uses the original popup's page to load the Jukebox page. The Jukebox page is supposed to be it's own popup.
The second argument to window.open is the windows name. You have both set to "popup". If a window by that name doesnt exist already, then oen is created, otherwise an existing one is used.
Just make sure those second args are different, and it should do the trick.