<script type="text/javascript">
        var fo = new SWFObject("viewer/viewer.swf", "viewer", "100%", "100%", "7", "#ffffff");   
        fo.addVariable("preloaderColor", "0xffffff");
        fo.addVariable("xmlDataPath", "site/path.php?g=mags");
        fo.addParam("wmode", "transparent")
        fo.write("flashcontent");   
    </script>

...where path.php is the page that dynamically generates the XML to permit multiple galleries:

$folder    =     $_GET[g];
$imgpath =     $folder."/";

include "../viewer/showconfig.php"

...the include pulls in the following to create the XML:

$imgpathup        = "../".$imgpath;

$number_of_pics = countfile($imgpathup);

echo "<?xml version='1.0' encoding='UTF-8'?>";

echo "<simpleviewerGallery maxImageWidth='701' maxImageHeight='1500' textColor='0x000000' frameColor='0xa9100c' frameWidth='2' stagePadding='10' thumbnailColumns='9' thumbnailRows='1' navPosition='top' title='Gallery' enableRightClickOpen='false' backgroundImagePath='' imagePath='$imgpath' thumbPath='$imgpath'>";

include "../viewer/showthumbs.php";
}

echo "</simpleviewerGallery>";

...showthumbs generates the XML for each image:

$picname=$i;
if ($i<10)
    {
    $picname='0'.$picname;
    }
if (file_exists($imgpathup.$picname.".jpg"))
    {
    echo "<image><filename>$picname.jpg</filename><caption>image $picname</caption></image>";   
    }

...and it all works fine in Mozilla Firefox without a hitch.