Copying a file to a network share, take 2

Hello, my app needs to copy a file on a network share. The network
share is accessible via a domain ID, which has all possible folder
rights assigned to it. I am using the impersonation code from here

http://msdn.microsoft.com/library/de...asp?frame=true

The code seems to properly impersonate (as evidenced by debug
statements), however, when I do this:

Dim sSource As String =
"\\nasrv88c3\modeldev$\modeldev\apps\web_inv\stmtstemp\MBS
Staging\ObjectList2.zip"
Dim sTarget As String =
"\\nasrv88c3\modeldev$\modeldev\apps\web_inv\stmtstemp\MBS
Staging\ObjectList.zip"

Try
File.Copy(sSource, sTarget)
Catch ex As Exception
MessageBox.Show(ex.ToString)
End Try

It fails with "System.Io.FileNotFoundException: Could not find the
file..." I know for sure that the file is there. Do I first perhaps
have to log on to the share? If so, are there any examples out there?
What am I missing in general?

Thank you