Blank Window with Internet Explorer

I'd need to know the actual JS error that's being fired and what function it's in. Without that there's not much to go on.

I've got the same error message.
Message: 'Drupal.settings.wysiwyg.configs' is null or not an object
Line: 4352
Char: 17
Code: 0
URI: "http://www.mysite/sites/default/files/js/js_a91f319ffefc667e2a24ada6530b..."

and this is the part of the code from the file js_a91f319ffefc667e2a24ada6530b42e6.js
line 4328 to 4367

/**
* Add additional Javascript to the page.
*/
Popups.addJS = function(js) {
// Parse the json info about the new context.
var scripts = [];
var inlines = [];
var src;
for (var type in js) if (js.hasOwnProperty(type)) {
if (type != 'setting') {
for (var file in js[type]) if (js[type].hasOwnProperty(file)) {
if (type == 'inline') {
inlines.push($(js[type][file]).text());
}
else {
src = $(js[type][file]).attr('src');
if (!Popups.originalJS[src.replace(/^(\/.+)\?\w$/, '$1')] && !Popups.addedJS[src]) {
// Get the script from the server and execute it.
$.ajax({
type: 'GET',
url: src,
dataType: 'script',
async : false,
success: function(script) {
eval(script);
}
});
// Mark the js as added to the underlying page.
Popups.addedJS[src] = 1;
}
}
}
}
}

// Add new JS settings to the page, needed for #ahah properties to work.
Drupal.settings = js.setting;

return inlines;
};

Maybe someone could help

I get the same problem with IE v9 (have not tested other versions of IE right now).
My setup:
Drupal 6.22
jQuery 1.2.6
jQuery Form Plugin 2.01
Popups 6.x-2.0-alpha6
Google Analytics is activated & locally cached (but not tracking page with popups)
---
Popups work with core js optimization turned off, when optimization is turned on, clicking on popups link shows loading .gif then blank page.
IE Error message is: Unable to get value of the property 'attr': object is null or undefined
popups.js, line 759 character 11
This is the line 759 of popups.js:
src = $(js[type][file]).attr('src');

I tried setting preprocess parameter to false (then cache, eventually both) in popups module file drupal_add_js() function (& drupal_add_css() function)
drupal_add_css(drupal_get_path('module', 'popups') .'/popups.css');
drupal_add_js(drupal_get_path('module', 'popups') .'/popups.js');
to
drupal_add_css(drupal_get_path('module', 'popups') .'/popups.css', 'module', 'all', FALSE);
drupal_add_js(drupal_get_path('module', 'popups') . '/popups.js', 'module', 'header', FALSE, FALSE, FALSE);

I did this to prevent the popups.js file from being aggregated (& cached) when the feature is turned on under performance section, but does not seem to be making any difference.