Internet Explorer cannot open Excel stream

[Christian W Larsen]

I want to export a datagrid to Excel. Here is the code:

[after datagrid databind]

Response.Clear();

Response.Buffer = true;
Response.AddHeader("content-disposition",
"attachment;filename=FileName.xls");
Response.ContentType = "application/vnd.ms-excel";
Response.Charset = "";
Response.Cache.SetCacheability(HttpCacheability.No Cache);
System.IO.StringWriter stringWrite = new
System.IO.StringWriter();
System.Web.UI.HtmlTextWriter htmlWrite = new
HtmlTextWriter(stringWrite);
DataGrid1.RenderControl(htmlWrite);
Response.Write(stringWrite.ToString());
Response.End();

When I open the page with Internet Explorer I get this:

Internet Explorer cannot download [file name] from [server name]
Internet Explorer was not able to open this Internet site. The
requested site is either unavailable or cannot be found. Please try
again later.

The funny thing: it works with Firefox - no problems at all.
Mime types on IIS are ok.