Offline Windows Update Using WUA in C# Error

Hi, I've get an error after calling of IUpdate2::CopyToCache() method in my
program. I trying to install windows updates (*.msu) at Windows Vista x86
with .NET program using WUA (as Interop.WUApiLib). My Code:
----------------------------------------------------
using System;
using System.Collections.Generic;
using System.IO;
using System.Diagnostics;
using WUApiLib;

namespace WUApiLibTest
{
static class Program
{
[STAThread]
static void Main()
{
// Update File: C:\Windows6.0-KB123456-x86.msu
// Emoty Directory: C:\ExpandedUpdate\
Process expandProcess = new Process();
expandProcess.StartInfo.FileName = "Expand";
expandProcess.StartInfo.WorkingDirectory = @"C:\";
expandProcess.StartInfo.Arguments =
@"C:\Windows6.0-KB123456-x86.msu -f:WSUSSCAN.cab C:\ExpandedUpdate\";
expandProcess.Start();
expandProcess.WaitForExit();

UpdateSessionClass updateSession = new UpdateSessionClass();
IUpdateServiceManager updateServiceManager =
updateSession.CreateUpdateServiceManager();
IUpdateService updateService =
updateServiceManager.AddScanPackageService("Offlin e Sync Service",
@"C:\ExpandedUpdate\WSUSSCAN.cab", 0);
IUpdateSearcher updateSearcher =
updateSession.CreateUpdateSearcher();
updateSearcher.ServerSelection = ServerSelection.ssOthers;
updateSearcher.ServiceID = updateService.ServiceID;
ISearchResult searchResult =
updateSearcher.Search("Type='Software'");

if (searchResult.Updates.Count > 0)
{
expandProcess.StartInfo.Arguments =
@"C:\Windows6.0-KB123456-x86.msu -f:Windows*.cab C:\ExpandedUpdate\";
expandProcess.Start();
expandProcess.WaitForExit();

StringCollectionClass filesToCopy = new
StringCollectionClass();
foreach (string fileName in
Directory.GetFiles(@"C:\ExpandedUpdate\", "Windows6.0-*.cab"))
filesToCopy.Add(fileName);
UpdateCollectionClass updateCollection = new
UpdateCollectionClass();
updateCollection.Add(searchResult.Updates[0]);
IUpdate2 iUpdate2 = (IUpdate2)searchResult.Updates[0];

// BUGGY LINE
iUpdate2.CopyToCache(filesToCopy);
// COMException (HRESULT: 0x80240026)
// 0x80240026 - WU_E_INVALID_UPDATE_TYPE

// ... updateInstaller etc.
}
}
}
}
----------------------------------------------------
Help me, please...
Best regards, Alexander Kozlenko

P.S. Sorry for my bad english.