IE overflow not scrolling on an absolute div

[pro120]

OK so here is the issue. Users on Internet Explorer with smaller screen resolutions are not able to scroll the pop up div that I have. Firefox 3 Safari Opera, and Chrome all recognize what to scroll on overflow. IE will come up with scrollbars but it does not scroll. Now I'm thinking a z-index issue might a problem but the overflow div is set to 100.

I gave the code here but here is the live link of my problem.
http://myharmonicwellness.com/calendar.php
[Click the Top Left Link in the calendar]
Shrink your window size to where the text begins to get cut off and you'll see the issue.

Here is the HTML for the popup. Keep in mind I have about 30 total of these popups embeded into one page.

<!--POPUP-->

<div id="workshop1" style="visibility:hidden;">
	<div id="fade"></div>

	<div class="popup_block">
	  <div class="popup">
			<a href="#" onclick="MM_changeProp('workshop1','','visibility','hidden','DIV')"><img src="images/icon_close.png" class="cntrl" title="Close" /></a>
			<h3><!--ONEPAGECMS-START-Workshop-1-Title-->
<p>Healing By Daring To Dream</p>
<!--ONEPAGECMS-END--></h3>
         <div class="workshopimg"><img src="/images/workshoppictures/healing_by_daring_to_dream.jpg" border="0"/>   </div>
<div class="des"><!--ONEPAGECMS-START-Workshop-1-Description-->
<p>Join author, Jodi Stauffer, and illustrator, Thom Ricks, for this inspired one day workshop.&nbsp; You will meet characters from their book, Dare to Dream, as they take you on a playful guided journey towards self-discovery that encourages you to be all that you've ever dreamed of becoming.&nbsp;</p>
<!--ONEPAGECMS-END--></div><br /> 
	  </div>
	</div>
</div>
<!--END POPUP-->

Here is the CSS

#fade {
	background: #000; 
	position: fixed; 
	width: 100%;
	height: 100%;
	filter:alpha(opacity=80);
	opacity: .80;
	-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=80)"; /*--IE 8 Transparency--*/
	left: 0;
	z-index: 10;
}

img {
	border: none;
}
.popup_block {
	float: left;
	width: 650px;
	max-height:80%;
	position: fixed;
	top: 10%;
	left: 50%;
	z-index: 200;
	background-color: #000000;
	-moz-border-radius: 15px;
	-moz-border-radius-topright: 0px;
	-webkit-border-radius: 15px;
	-webkit-border-top-right-radius: 0px;
	border: 1px solid #FFFFFF;
	filter:alpha(opacity=100);
	-moz-opacity:1;
	-khtml-opacity: 1;
	opacity: 1;
	margin-top: 0;
	margin-right: 0;
	margin-bottom: 0;
	margin-left: -335px;
	padding-top: 10px;
	padding-right: 20px;
	padding-bottom: 10px;
	padding-left: 20px;
	overflow: auto;
}
.popup {
	float: left;
	width: 100%;
	margin: 10px 0;
	padding: 10px 0;
	color: #FFFFFF;
}
*html #fade {
	position: absolute;
	top:expression(eval(document.compatMode &&
	document.compatMode=='CSS1Compat') ?
	documentElement.scrollTop : document.body.scrollTop);
}

*html .popup_block {
	position: absolute;
	top:expression(eval(document.compatMode &&
	document.compatMode=='CSS1Compat') ?
	documentElement.scrollTop
	+((documentElement.clientHeight-this.clientHeight)/2)
	: document.body.scrollTop
	+((document.body.clientHeight-this.clientHeight)/2));
	
	left:expression(eval(document.compatMode &&
	document.compatMode=='CSS1Compat') ?
	documentElement.scrollLeft 
	+ (document.body.clientWidth /2 ) 
	: document.body.scrollLeft 
	+ (document.body.offsetWidth /2 ));
}

/*--IE 6 PNG Fix--*/

img{ behavior: url(iepngfix.htc) }

#workshop1 {
	position: absolute;
	width: 100%;
	height: 100%;
	top: 0;
	left: 0;
}

[pro120]

Turned out to be a "DUH" answer. IE doesn't recognize fixed position divs. Changed to absolute and now working. Thanks for the help.........