Prima utilizzavo questo codice... Il secondo, credevo mi avrebbe risolto il problema, ma così non è stato...

<%
path = session("A")
nomegiusto = session("nomegiusto")

Dim objStream
Set objStream = Server.CreateObject("ADODB.Stream")
objStream.Type = 1
objStream.Open()

set file = Server.CreateObject("Scripting.FileSystemObject")
adReadAll = -1

if file.FileExists(path) then
objStream.LoadFromFile (path)
Response.Buffer = true
Response.Expires = 0

strFileType = "."
strFileType = strFileType & session("ext")

Select Case strFileType
Case ".doc"
ContentType = "application/msword"
Case ".xls"
ContentType = "application/vnd.ms-excel"
Case ".pdf"
ContentType = "application/pdf"
Case ".ppt"
ContentType = "application/vnd.ms-powerpoint"
Case ".gif"
ContentType = "image/gif"
Case ".jpg"
Case ".jpe"
Case ".jpeg"
ContentType = "image/jpeg"
Case ".bmp"
ContentType = "image/bmp"
Case ".zip"
ContentType = "application/zip"
Case ".htm"
Case ".html"
ContentType = "text/html"
Case Else
ContentType = "application/octet-stream"
End Select

Response.ContentType = ContentType
Response.Addheader "Content-Disposition", "attachment; filename=" & nomegiusto
Response.Addheader "Content-Length", objStream.size
Response.BinaryWrite(objStream.Read(adReadAll))
Response.Flush
end if

objStream.Close
Set objStream = Nothing
%>