Call Vb.Net Developed Dll In SQL Server 2005 With Configuration Level 80 Then Gets Error Invalid Class String

Hi,
I want to call a dll from Stored procedure developed in SQL Server 2005 at configuration level 80. but when I execute the stored procedure I get the following error.

Error Source: ODSOLE Extended Procedure
Description: Invalid class string

Code of stored procedure and vb.net class is given below:

VB.Net
Imports System
Imports System.IO
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.SqlTypes
Imports Microsoft.SqlServer.Server
Imports Microsoft.VisualBasic
Imports System.Diagnostics

Public Class PositivePay

Public Shared Sub LogToTextFile(ByVal LogName As String, ByVal newMessage As String)
' impersonate the calling user
Dim newContext As System.Security.Principal.WindowsImpersonationContext
newContext = SqlContext.WindowsIdentity.Impersonate()
Try
Dim w As StreamWriter = File.AppendText(LogName)
LogIt(newMessage, w)
w.Close()
Catch Ex As Exception

Finally
newContext.Undo()
End Try
End Sub
End Class
===============================================================

STORED PROCEDURE
Create PROCEDURE [dbo].[PPGenerateFile]
AS

BEGIN
Declare @retVal INT
Declare @comHandler INT
declare @errorSource nvarchar(500)
declare @errorDescription nvarchar(500)
declare @retString nvarchar(100)

-- Intialize the COM component
EXEC @retVal = sp_OACreate 'PositivePay.class', @comHandler OUTPUT
IF(@retVal <> 0)
BEGIN
--Trap errors if any
EXEC sp_OAGetErrorInfo @comHandler,@errorSource OUTPUT, @errorDescription OUTPUT
SELECT [error source] = @errorsource, [Description] = @errordescription
Return
END

-- Call a method into the component
EXEC @retVal = sp_OAMethod @comHandler,'LogToTextFile',@retString OUTPUT, @LogName = 'D: ext.txt',@newMessage='Hello'
IF (@retVal <>0 )
BEGIN
EXEC sp_OAGetErrorInfo @comHandler,@errorSource OUTPUT, @errorDescription OUTPUT
SELECT [error source] = @errorsource, [Description] = @errordescription
Return
END
select @retString

END