per capire dove si ferma, metti qualche response write


...

Response.Write c_att(i) ' <<<<<<<<<<<<<<<<<
If Not (c_att(i)="Attach.") Then
For Each objFile in colFiles
Response.Write objFile.Name ' <<<<<<<<<<<<<<<<<
Response.Write prefix ' <<<<<<<<<<<<<<<<<
if InStr(1, objFile.Name, prefix, 1) > 0 then objFile.Delete
Next
End If