cannot see bgiframe enable in firefox and IE 7/8 (Windows XP & 2003)

cannot see bgiframe enable in firefox and IE 7/8 (Windows XP & 2003)

hi,

I have a simple dialog like below

        $("#please-wait").dialog({ width: 60, height: 130, modal: true, resizable: false, autoOpen: false, bgiframe: true,
            open: function (event, ui) {
                $(".ui-dialog-titlebar").hide();
            },
            close: function (event, ui) {
                $(".ui-dialog-titlebar").show();
            }
        });

I only see bgiframe work on IE 8 & Windows 7 (my computer), in fact that IFRAME tag always above tittle div and content div:
      <DIV    ui-dialog>
            <IFRAME>    <--- this is bgiframe
            <DIV      ui-title>
            <DIV      ui-content> 
       </DIV>

I try with IE 7/8 on others windows platform (XP, 2003) and firefox, I cannot see IFRAME tag like what I see on IE8 & Window7.

Please help me to solve this problem.