Impersonation Problem

[velvet.graham]

I'm having a difficult time with impersonation. I've created an
impersonation class. Here is the code below:

******Impersona tion Class Code*********
Imports System
Imports System.Web.Secu rity
Imports System.Runtime. InteropServices
Imports System.Security .Principal
Imports System.Director yServices
Imports System.Security .Permissions
Public Class SecurityHelpers
Private Sub New()
MyBase.New()

End Sub

Declare Auto Function LogonUser Lib "advapi32.d ll" (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
Declare Auto Function CloseHandle Lib "kernel32.d ll" (ByVal handle
As IntPtr) As Boolean

Public Shared Function CreateIdentity( ByVal userName As String,
ByVal domain As String, ByVal password As String) As WindowsIdentity
Dim tokenHandle As IntPtr = New IntPtr(0)
Const LOGON32_PROVIDE R_KERBEROS As Integer = 3
Const LOGON32_LOGON_I NTERACTIVE As Integer = 2
tokenHandle = IntPtr.Zero
Dim returnValue As Boolean = LogonUser(userN ame, domain,
password, LOGON32_LOGON_I NTERACTIVE, LOGON32_PROVIDE R_KERBEROS,
tokenHandle)
If (False = returnValue) Then
Dim ret As Integer = Marshal.GetLast Win32Error
Throw New System.Unauthor izedAccessExcep tion(("LogonUse r
failed with error code: " + ret))
End If
Dim id As WindowsIdentity = New WindowsIdentity (tokenHandle)
CloseHandle(tok enHandle)
Return id
End Function
End Class

*********Here is how I'm calling it in my code:*********

Dim wic As WindowsImperson ationContext = Nothing
wic = SecurityHelpers .CreateIdentity (username, domain,
password).Imper sonate
'Upload the file
wic.undo

The error only occurs when I'm on trying to access resources on another
server. I can upload a file to the other server, but I can't access any
of the file's properties. Here is the error below:

********Error** *********
Impersonation failure.
Description: An unhandled exception occurred during the execution of
the current web request. Please review the stack trace for more

information about the error and where it originated in the code.

Exception Details: System.Web.Http Exception: Impersonation failure.
Portion of stack trace:
HttpException (0x80004005): Impersonation failure.]
System.Web.Impe rsonationSuspen dContext.GetCur rentToken() +215
System.Web.Impe rsonationSuspen dContext.Suspen d() +53
System.Web.Http Context.GetConf ig(String name) +104

System.Web.Conf iguration.HttpC onfigurationSys temBase.System. Configuration.I ConfigurationSy stem.GetConfig( String
configKey) +22
System.Configur ation.Configura tionSettings.Ge tConfig(String
sectionName) +69
System.Configur ation.Configura tionSettings.ge t_AppSettings() +26

I would appreciate any help you could give me. Thanks.