overflow:auto makes the swf disappear in firefox

on clicking one of 3 tabs with this code

<span onclick="change_page('1')" </span>

This javascript function below hides a couple of <div> groups of content and shows the one

specified by the page_number passed in as a parameter.

function change_page(page_number){
document.getElementById('content_group1').style.visibility = "hidden";
document.getElementById('content_group2').style.visibility = "hidden";
document.getElementById('content_group3').style.visibility = "hidden";

document.getElementById('content_group'+page_number).style.visibility = "visible";
}

The 'content_group's have the class .group and the #ids shown and are styled with the css

below (I need auto for the overflow because the content in the groups is fed from xml/xsl and

can be of any size, the number of pages also varies (fed from xml/xsl). I have provided code

here for the 3 page case as an example.)

.group
{
position: absolute;
top:25px;
border:solid 1px;
border-color:#000;
border-bottom-color:#ccc;
border-right-color:#ccc;
padding-top:10px;
background-color:#ececdb;
width:740px;
height:450px;
overflow:auto;
}

#content_group1{}
#content_group2{visibility: hidden;}
#content_group3{visibility: hidden;}

Works fine as tabbed pages on a webpage in IE, apart from flash content in firefox . Here,

the flash does not appear, unless (teasingly) the flash is in the last content group i.e. the

third one in the case given above(I'm sure that's a clue )

Take away the auto on overflow and it works fine all round. But we like the auto on the

overflow. Can you help?