error on httpwebrequest:The 'Host' header cannot be modified directly. Parameter name: name

Question

I realize that this cannot be modified according to previous posts but if this is set in the actual header; would it not be necessary to include it in the httpwebrequest header as well. Also the actual header includes X-Requested-With:XMLHTTPRequest so I realize this may be a dumb question but how do you include this in the httpwebrequest header. I got back some response without using it.

Also when I now include other parameters the request hangs at

Dim response As HttpWebResponse = DirectCast(webRequest.GetResponse(), HttpWebResponse)

indefinitely...Now I used to get a response before I included the following parameters which are in the actual request header:

webRequest.Method = method__1.ToString()
            webRequest.ServicePoint.Expect100Continue = true
            webRequest.ContentType = "application/x-www-form-urlencoded"
            webRequest.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.6) Gecko/20100625 Firefox/3.6.6 GTB7.1 ( .NET CLR 3.5.30729; .NET4.0E)"
            webRequest.KeepAlive = True
            webRequest.AllowAutoRedirect = False
            webRequest.ContentLength = 19
            webRequest.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"
            ***webRequest.Headers.Add("Cookie", cookielogin)
            webRequest.Headers.Add(HttpRequestHeader.CacheControl, "no-cache")
            webRequest.Headers.Set(HttpRequestHeader.AcceptLanguage, "en-us,en;q=0.5")
            webRequest.Headers.Set(HttpRequestHeader.AcceptEncoding, "gzip,deflate")
            webRequest.Headers.Set(HttpRequestHeader.AcceptCharset, "ISO-8859-1,utf-8;q=0.7,*;q=0.7")
            webRequest.Referer = "http://www"***

Any help appreciated.