Response.WriteFile Error With Word Documents

I'm working on a project where a Word document is generated dynamically, then is streamed to the user via the Response.WriteFile command, but I'm running into some problems. The exact same code works for my .pdf file, but for some reason I encounter weird errors with .doc files. Here's the code:

 

Protected Sub btnDoc_Click(ByVal s As Object, ByVal e As ImageClickEventArgs) Handles btnDoc.Click

btnSave_Click(s, e)

Try

_oConn.Open()

Dim Contract As New Contract(_oConn, _ContID)

Dim Artist As New Artist(_oConn, Contract.ArtID)

Dim Promotion As New Promotion(_oConn, Contract.PromID)

Dim Venue As New Venue(_oConn, Contract.VenID)

Dim Doc As New Doc

Try

Doc.Open(Server.MapPa ...