Why does IE fail to server my CSV file from Response.Write

Response.Clear();

 Response.ContentType = "text/CSV";

 Response.CacheControl = "no-cache";
 Response.AddHeader("Pragma", "no-cache");
 Response.Expires = -1;

 Response.AddHeader("Pragma", "must-revalidate");
 Response.AddHeader("Cache-Control", "must-revalidate");
 Response.AddHeader("Accept-Header", csvResults.Length.ToString());
 Response.AddHeader("Content-Length", csvResults.Length.ToString());
 Response.AddHeader("content-disposition", "attachment; filename=test.csv");
 Response.Write(csvResults.ToString());
 Response.Flush();
 Response.End();

protected void Application_BeginRequest(Object sender, EventArgs e)
    {
        string requestURL = Request.Url.ToString().ToLower();
        if (requestURL.StartsWith("http://"))
        {
            Response.Redirect(requestURL.Replace("http:", "https:"));
        }
    }

HTTP/1.1 200 OK
Date: Tue, 09 Nov 2010 14:23:50 GMT
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
X-AspNet-Version: 4.0.30319
Pragma: no-cache
Pragma: must-revalidate

content-disposition: attachment; filename="test.csv"
Cache-Control: no-cache
Pragma: no-cache
Expires: -1
Content-Length: <length value would be here>
Content-Type: text/CSV

"COL1","COL2","COL3"
"VAL1","VAL2","VAL3"
"VAL1","VAL2","VAL3"
"VAL1","VAL2","VAL3"

Response.ClearHeaders();
Response.AddHeader("Cache-Control", "no-store, no-cache");