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.AddHea der("content-disposition",
"attachment;fil ename=FileName. xls");
Response.Conten tType = "applicatio n/vnd.ms-excel";
Response.Charse t = "";
Response.Cache. SetCacheability (HttpCacheabili ty.NoCache);
System.IO.Strin gWriter stringWrite = new
System.IO.Strin gWriter();
System.Web.UI.H tmlTextWriter htmlWrite = new
HtmlTextWriter( stringWrite);
DataGrid1.Rende rControl(htmlWr ite);
Response.Write( stringWrite.ToS tring());
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.