Prompted for login when launching Excel ?

Guys,

I launching excel through an ASP page to send data to a workbook then save it down. Problem is, I am being prompted for a network login when trying to do this . . .

Dim oExcel As New Excel.Application

If I login as a domain admin, the code works fine, otherwise I cant get access and cancelling the login debugs on this line.

note : I have Identity Impersonate on in the web.config file for other reasons.

Any ideas ?

Thanks
Bob