WCF type init DiagnosticUtility failed

What is the reason for the WCF error message
"Der Typeninitialisierer für System.ServiceModel.DiagnosticUtility hat eine
Ausnahme verursacht."
(WCF type init DiagnosticUtility failed) ?

created by the line
myServiceHost = New ServiceHost(GetType(CalculatorService))

and
Imports System.ServiceModel
Imports Contracts

Public Class CalculatorService
Implements ICalculator

Public Function Add(ByVal operand1 As Integer, ByVal operand2 As
Integer) As Integer Implements Contracts.ICalculator.Add
Return operand1 + operand2
End Function
End Class


thank you very much