I believe I isolated the issue. Please open up your dnn.xmlhttp.js file in the js folder and change the following function (approx line 109)
dnn_xmlhttp.prototype.XmlHttpRequest.prototype.onreadystatechange = function ()
{
if (this.statusFunc != null)
this.statusFunc(this._request.readyState, this.context);
if (this._request.readyState == '4')
{
this.complete(this._request.responseText);
this._request.onreadystatechange = new function() {};//stop IE memory leak. Not sure why can't set to null;
}
}
Let me know if this fixes the issue for you so I can release an appropriate patch.