I have seen this problem before and managed to work around it by modifying the HTTP headers, but I can't remember exactly what I did. Try sending a content-length header, specifying the size of your file.
Sent by on 08/15/2006 11:19:30 AM:
Small issue with the following. It works, but when the File Download window pops-up and I click on "Open" another (almost) exact pop-up appears. The only difference is that the "Always ask before opening this type of file" checkbox at the bottom is not grayed-out on the second one. The second one will actually open the download file. The first one works as exepected if I click on "Save" or "Cancel" so why would clicking on "Open" cause the second window to pop-up?
Response.AddHeader("Content-Type", "application/ms_excel") Response.AddHeader("Content-Disposition", "attachment; filename=Principal_Download.xls") cOutput = m.ExcelData Response.Write(cOutput)