Modal Popup with Drop Down lists

I am trying to display a modal popup on a page with drop down lists. When I display a modal popup, drop down lists are not disables. I can still select them. Is there any way to disable them?

ThanksPlease see FAQ number 15 (http://forums.asp.net/thread/1293293.aspx); you may need to manually disable the drop down lists when the ModalPopup is active.