global_start sessions & ie7

[x3lite]

I created a plugin, hook location: global_start, added code, and enabled it.

PHP Code:


session_start();
if (is_null($_SESSION['myadsession']))
{
$_SESSION['myadsession'] = 'No';

$showad = '<img src="http://example.com/ad.gif">';
}
else
{

} 


And I added to style footer:

PHP Code:

$showad 


The ad shows once per session in firefox.
IE7 doesn't show it...


Any ideas?
The similar php code works on some of my other sites [non-forums]...


Thanks,