Output to Excel 2007

The following code used to outputs to Excel 2003 fine. Do I need to change it
to output to Excel 2007?
<%
Response.ContentType = "application/vnd.ms-excel"
Response.AddHeader "Content-Disposition", "attachment; filename=List.xls"
%>

In addition, it pops a small File Download - Security Warning window showing
the Name: List.xls
Type: MS Excel 97-2003 Worksheet, 2.66 MB
and it displays the output in Excel fine.

But other times it it pops a small File Download - Security Warning window
showing the
Name: MyAspPage_asp (instead of List.xls)
Type: MS Excel 97-2003 Worksheet, 416 bytes
and when I click on Save it shows error:
IE cannot download MyAspPage.asp
and if I click Open instead of Save it will pop up a small Microsoft Office
Excel window with the following error:
"Microsoft Excel cannot access the file
'https://www.myurl.com/dir1/MyAspPage.asp'. There are several possible
reasons:
- The file name or path name does not exist.
- The file you're trying to open is being used by another program. Close
the document in the other program, and try again.
- The name of the workbook you're trying to save is the same as the name
of another document that is read-only. Try saving the workbook with a
different name."