Modal Popup

Well, I have no hair left to pull out after two solid days of trying to display an add window in a modal popup. I believe I have read every post on the subject multiple times and followed the instructions a best as I can (I am not a practiced javascript coder.....) and I still cannot get the popup to appear.
I have enabled all popups in the browser (Chromium and FireFox), I do not see any javascript errors being generated, I can see the function being called, but nothing appears on the screen!
I have created the following javascript file called MigTools10.js:

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function displayPopup(params)
{
var pageid=1;
var pageObj = Runner.pages.PageManager.getById(pageid);
args = {
bodyContent: "<iframe frameborder='0' id='popupIframe" + pageid + "' style='width: 100%; height: 100%; border: 0;'></iframe>",
footerContent: "<span> </span>",
headerContent: params.headerContent,
centered: true,
render: true,
width: params.width ? params.width : 450,
height: params.height ? params.height : 315
},
afterCreateHandler = function(win) {
var bodyNode = $(win.bodyNode.getDOMNode()),
iframeNode = $("iframe#popupIframe" + pageid, bodyNode);

iframeNode.load(function() {
if (Runner.isChrome) {
bodyNode.addClass("noScrollBar");
}
win.show();

}).attr("src", params.url);
},
afterCloseHandler = params.afterClose;

if (Runner.isChrome) {
$("< style type='text/css'> .yui3-widget-bd::-webkit-scrollbar {display:none;} < /style>").appendTo("head");
}

Runner.pages.PageManager.createFlyWin.call(pageObj, args, true,
afterCreateHandler, afterCloseHandler);
}

function select_env()
{
params =
{
url: 'MIGTOOLS_SELECT_ENV_add.php',
afterClose: function(win)
{
win.destroy(true);
},
headerContent: 'Select Connection'
};

displayPopup(params);
}

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and placed the following in the header option on the editor tab (Version 10):

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<script src="MigTools10.js" type="text/javascript"></SCRIPT>

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Then in the Client Before event of a custom button on a list page I have this:

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select_env();

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As I said - I can see this function being called and apparently without any errors, so why does the popup not appear?

Thanks for the help.....