Okay, in the end I didn't use either of your suggestions, but crafted
my own based on some API documentation I read through.

Below is my solution if any future archive browsers need it:

//////////////////
Imports System.Security.Principal
Imports System.Runtime.InteropServices

Public Class MyClassToBeThreaded

   <DllImport("advapi32.dll")> _
   Protected Shared Function LogonUser(ByVal lpszUserName As String,
_
                                   ByVal lpszDomain As String, _
                                   ByVal lpszPassword As String, _
                                   ByVal dwLogonType As Integer, _
                                   ByVal dwLogonProvider As Integer,
_
                                   ByRef phToken As IntPtr) As
Boolean
   End Function

   '// This is the thread to be called asynchronously,
   '// so do the impersonation calls here
   Public Sub DoTheWork()
       Try
           Dim hToken As IntPtr
           If LogonUser("username", "domain", "password", 2, 0,
hToken) Then
               Using wi As WindowsIdentity = New
WindowsIdentity(hToken), wic As WindowsImpersonationContext =
wi.Impersonate()
                   '// Do the actually work here

               End Using
           End If
       Catch
           '// Handle the exception if the impersonation
           '// blows up in your face :-)
       End Try
   End Sub

End Class
/////////////////////

Thanks,

Seth Rowe