If you have the ability to recompile your code then can you try the following "fix", which should trap the error and allow you to log off.

In UserModuleBase.vb, at the end of the method LookupCountry().

Replace

            'Get the country code based on the IP address
           Return _CountryLookup.LookupCountryName(IP)

By

            'Get the country code based on the IP address
            Dim country As String = Null.NullString
            Try
                country = _CountryLookup.LookupCountryName(IP)
            Catch ex As Exception
                LogException(ex)
            End Try
            Return country
 

Unfortunately I cannot test this as I cannot duplicate the problem.