Popup layer vanishes when scrolling page in FireFox

I've noticed a quirk with Firefox that does not appear to occur in IE, Opera, nor Safari. When clicking on a button that pops up a layer (with a text object and embedded YouTube video), the popup layer vanishes if I use the vertical scroll bar, just as if I clicked on an object outside of the layer.

Is there a way to prevent this?

Thanks.

You need to LOCK the popup layer.

Please read item 10 here

► http://www.talkgraphics.com/showthread.php?t=45105

Thanks, SLedger... looks like that would do the trick for me.