Hello Peter,

I have test with the following steps, but cannot reproduce the issue in my
side.

1.Write an Excel AddIn(I write in managed codes, but I think that should
not be related to the problem)
--------------------Codes--------------------------------
private void ThisAddIn_Startup(object sender, System.EventArgs e)
{
this.Application.WorkbookOpen += new
Microsoft.Office.Interop.Excel.AppEvents_WorkbookO penEventHandler(Applicatio
n_WorkbookOpen);
}

void
Application_WorkbookOpen(Microsoft.Office.Interop. Excel.Workbook Wb)
{
MessageBox.Show(Wb.Name);
}
---------------------------------------------------------------

2.Upload a test.csv file into my sharepoint site.

3.Open an IE to navigate to the test.csv file's url
(http://devforum/Temp/test.csv)

4.I see a messagebox popup before the csv file is opened in a new created
Excel instance.

I think the difference may be from,
1. The Excel version. (The event implementation may have some changes to
cause the issue.) In my side, I use the Office 2007 with SP2 and all
updates.
2. The Internet Explorer version( This process involves some actions with
IE. So how IE to download and start an Excel, open Workbook can be
different ). I am using IE8 at my side.

So could you please clarify your environment for a future investigation on
the issue?



Best regards,
Ji Zhou
Microsoft Managed Newsgroup Support Team