Saxon Process is not releasing my output file

Hope this is an "in Scope" question. I'm using Saxon to run a process
in .net. The basic scenario is my xslt takes an XML called new,
compares it to an XML document called old. Then the "new" XML document
is copied over "old".

The problem is when the copy happens I get the dreaded "The process
cannot access the file 'L:\file_path\old.xml' because it is being used
by another process".

Dim x As New Saxon
x.Transform(strDir & "my.xsl", strDir & "new.xml", strRepository &
"difference.xml")
x = Nothing

' Error occurs here
File.Copy(strDir & "Stat.xml", strDir & "stat_old.xml", True)

The Transform: (probably more Nothing/Flush/Close commands then I need
but I wanted to make sure everything was taken care of):

      Public Sub Transform(ByVal xslDoc As String, ByVal xmlDoc As String, _
           ByVal output As String)

           Dim u As Uri
           'Create a New Processor instance
           Dim processor As New Processor
           'Load the source document
           u = New Uri(xmlDoc)
           Dim input As XdmNode = processor.NewDocumentBuilder.Build(u)
           'Create the transformer for the stylesheet
           Dim transformer As XsltTransformer

           Try
               u = New Uri(xslDoc)

               transformer = _
                   processor.NewXsltCompiler().Compile(u).Load()
           Catch ex As Exception
               u = Nothing
               MsgBox("Exception" & ex.ToString)
               MsgBox(ex.StackTrace)
               Throw New Exception(ex.Message)
           End Try

           'Set the root node of the source document to be the
initial context node
           transformer.InitialContextNode = input

           'Create the serializer
           Dim serializer As New Serializer
           Dim fi As FileStream
           Try
               fi = New FileStream(output, FileMode.Create, FileAccess.Write)
               serializer.SetOutputStream(fi)
               'Transform the source XML
               transformer.Run(serializer)
               'fi.Flush()
               'fi.Dispose()
               fi.Close()
           Catch ex As Exception
               Throw New Exception(ex.Message)
           Finally
               u = Nothing
               serializer = Nothing
               transformer = Nothing
               processor = Nothing
               input = Nothing
               fi = Nothing
           End Try