Why SparkWeb restarts in div element after javascript display change

Hi all,

SparkWeb is working absolut fine but restarts if the surrounding div element is set to display: none and back to display: block

This is the way i used it in the page (autologin is enabled):

<div class="window-content" style="margin: 0; padding: 0; padding: 5px 0px 0px 0px;" id="spark"> <iframe name="chat" src="URL_TO_SparkWeb.htm" frameborder="0" scrolling="no" width="100%" height="500px"></iframe>
</div>

A Button has the following Javascript:

document.getElementById('spark').style.display='none';

Another Button has this Javascript:

document.getElementById('spark').style.display='block';

Why is SparkWeb restarting the flash and i lose connection after the element is set back visible … and is there a possibility to keep chat alive after the div element was set back visible.

Thanks for your help !

I set up a testpage (not w3c but for tests ok ) : http://85.114.128.164/sparkwebtest/
(The iframe is not the problem, i tested it with and without !)

Only FF2 and FF3 have problems … IE6 and IE7 working fine.

Is there a way to fix this behavior in FF?