AJAX :: Modal User Control On Top Of A Modal Popup + Javascript Causes Page Flash

Modal Popup user control (its a message box) on top of a modal popup with javascript that maintains postback on a scrollable div all inside of an update panel causes my page to flash on postback of the user control. If any one of the peices (user control, modal popup, javascript) are missing everything works fine. The javascript is maintaing scrollback on a scrollable listview on the page. A modalpopup is shown on top of this main page that is for report parameters. The user control is used for validation and is displayed if a parameter is invalid. I know this may not be the best design, but it can't really change unless its a minor change. Heres the js if anyone wants to see popup or styles let me know.

//Begin methods to maintain or reset scroll position during postback.
var controlIds = [];
var scrollTops = [];
//Register a control to maintain its scroll position on postbacks.
function MaintainPostback(controlId) {
controlIds.push(controlId);
}
//Find the div/control id in the controlIds array and set its scroll position to 0.
function ResetControlScrollTop(controlId) {
var index = 0;
while (index < controlIds.length) {
if (controlId == controlIds[index]) {
scrollTops[index] = 0;
return;
}
index++;
}
}............