WCF Remote Calling method error: The type initializer for 'GlobalUSSFService.USSFService' threw an exception.

Hi,
Thanks for the reply, and here is my class.

Imports System.DirectoryServices.AccountManagement
Imports System.Data.SqlClient

Partial Public Class USSFService
Implements ISFUser

'Private Shared SFUserId As String

'Private Shared SFUsersGroup As String = "ILHSPR"
'Private Shared SFAdminGroup As String = "Administrators"
'Private Shared SFSalesGroup As String = "TDSales"

Private Shared SFUsersGroup As String = "SOFTDEV"
Private Shared SFAdminGroup As String = "SOFTDEV"
Private Shared SFSalesGroup As String = "SOFTDEV"
Private Shared TDPrincipalContext As PrincipalContext = New PrincipalContext(ContextType.Domain, "XXXX")

Public Function GetAllProofReaders() As System.Collections.Generic.List(Of String) Implements ISFUser.GetAllProofReaders
Dim group As GroupPrincipal = GroupPrincipal.FindByIdentity(TDPrincipalContext, IdentityType.SamAccountName, SFUsersGroup)
Dim proofreaders As List(Of String) = New List(Of String)

For Each member As Principal In group.Members
If Not TypeOf member Is GroupPrincipal Then
If CType(member, UserPrincipal).Enabled Then proofreaders.Add(member.SamAccountName)
End If
Next
proofreaders.Sort()
Return proofreaders
End Function
End Class

i'm trying to access this method, which is working file when i host it locally.
But when i host it on a remote system and trying to call this method i got this exception.

and inner exception says 'Nothing'