C# / VB.NET - crittografia con vs2005

ho un problema.il codice cripta bene i file .txt ma con gli altri formati di testo non mantiene il formato al decriptare.il codice è:

Function AES(ByVal sInputFilename As String, ByVal sOutputFilename As String, ByVal sKey As String)

        Dim vAES As New RijndaelManaged
        ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
        vAES.BlockSize = 128
        vAES.KeySize = 128
        vAES.Key = ASCIIEncoding.ASCII.GetBytes(sKey)
        vAES.IV = ASCIIEncoding.ASCII.GetBytes(sKey)
        ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
        If FlagCriptDecript Then
            Dim FileInputCript As New FileStream(sInputFilename, FileMode.Open, _
                                         FileAccess.Read)
            Dim FileCriptado As New FileStream(sOutputFilename, FileMode.Create, _
                                                 FileAccess.Write)
            Dim Encriptador As ICryptoTransform = vAES.CreateEncryptor()
            Dim FlujoCriptado As New CryptoStream(FileCriptado, Encriptador, _
                                                  CryptoStreamMode.Write)
            Dim ArrayByteInput(FileInputCript.Length - 1) As Byte
            ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
            FileInputCript.Read(ArrayByteInput, 0, ArrayByteInput.Length)
            FlujoCriptado.Write(ArrayByteInput, 0, ArrayByteInput.Length)
            ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
            FlujoCriptado.Close()
            FileInputCript.Close()
            ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
        ElseIf Not FlagCriptDecript Then
            Dim FileInputDecript As New FileStream(sInputFilename, FileMode.Open, _
                                                   FileAccess.Read)
            Dim Decriptador As ICryptoTransform = vAES.CreateDecryptor()
            Dim FlujoDecriptado As New CryptoStream(FileInputDecript, Decriptador, _
                                                    CryptoStreamMode.Read)
            Dim FileDecriptado As New StreamWriter(sOutputFilename)
            ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
            FileDecriptado.Write(New StreamReader(FlujoDecriptado).ReadToEnd)
            FileDecriptado.Flush()
            ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
            FileInputDecript.Close()
            FileDecriptado.Close()
            ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
        End If
        ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
        FlagCriptDecript = False
        ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    End Function

cosa sbaglio????