HTTPS - Why cannot retrieve application such as pdf, word, powerpoint etc via https!?

Hi there
Here is the scenario:
We can upload any type of the files via http or https to server and store them in our database. We also can successfully retrieve the files from the database and save them into the disc in the server(for testing).
BUT the server ONLY manage to send the IMAGES to Client browser and it fails if the file is an APLLICATION such as PDF, Word, PowerPoint etc. This problem occurs if we try to view the file via https however it is okey if we view them using http.

This is how we are getting the content of the file from the DB and sending it to client browser in ASP page. I have to mention that it works very well for any type of the files via HTTP:
 ...
  Response.ContentType = Mimetype   'eg:  "image/jpeg"

 set rs = EclairConnection.Execute( qryContent )
If Not rs.Eof then
      size = (4 * 1024) '4K
      set aField = rs(0)      
      chunk= aField.GetChunk(100)
      do while not isnull(chunk)                        
            Response.BinaryWrite chunk
            chunk = aField.GetChunk(size)
      loop                        
End If
set rs = nothing



So my Ques:
I was wondering if any setting needs to be changed in firewall (SSL) to avoid this problem?
OR
Do I need to add a special header in my ASP page using AddHeader method ?
OR
What do you think?

Cheers