HttpWebRequest incorrect 404

[Steven Hackney]

Hi.
I've encountered a strange problem.
I wrote the following routine:

HttpWebRequest wr = (HttpWebRequest)WebRequest.Create(url);
wr.Method = "GET";
wr.Timeout = 5000; // 5 seconds should be plenty
wr.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; .NET CLR
1.0.3705)";
wr.AllowAutoRedirect = true;
wr.CookieContainer = new CookieContainer();
WebResponse wResp = wr.GetResponse();

Most of the time this is fine. But occationally I come across an address
like
http://www.topcar.com/frame.html
which generates a 404 exception.
However, if you open it up in IE everything is fine.

Anybody got any ideas as to what it is that I'm doing wrong?

Steven