Erro ao executar query no WorkFlow para localizar e-mail na fila.

Question

         Bom dia a todos ,

estou com um problema em um metodo onde eu tento localizar o [QueueItemId] de um [email] na [queueitem]. Mas na hora de exexutar o comando [BusinessEntityCollection _Bec = service.RetrieveMultiple(_Query);] ele da uma [Exception]

Obs: esse erro so ocorre qndo eu rodo o metodo [getQueueIDByEmail] não ocorre para o metodo [getEmailByRegardindID] 


Alguem saberia me ajudar?   
Grato.


Codigo dos 2 metodos:
 
        private queueitem getQueueIDByEmail(Guid guid, ICrmService service)
        {

            QueryExpression _Query = new QueryExpression();
            _Query.EntityName = "queueitem";
            _Query.ColumnSet = new AllColumns();

            ConditionExpression _ce1 = new ConditionExpression();

            _ce1.AttributeName = "objectid";
            _ce1.Operator = ConditionOperator.Like;
            _ce1.Values = new object[] { guid.ToString() };

            FilterExpression _FilterExpression = new FilterExpression();
            _FilterExpression.FilterOperator = LogicalOperator.And;
            _FilterExpression.Conditions.Add(_ce1);

            _Query.Criteria = _FilterExpression;
            BusinessEntityCollection _Bec = service.RetrieveMultiple(_Query);

            queueitem oQueue = null;

            if (_Bec.BusinessEntities.Count > 0)
            {
                oQueue = _Bec.BusinessEntities[0] as queueitem;
            }

            return oQueue;

        }

        private email getEmailByRegardindID(Guid guid, ICrmService service)
        {
            QueryExpression _Query = new QueryExpression();
            _Query.EntityName = EntityName.email.ToString();
            _Query.ColumnSet = new AllColumns();

            ConditionExpression _ce1 = new ConditionExpression();

            _ce1.AttributeName = "regardingobjectid";
            _ce1.Operator = ConditionOperator.Like;
            _ce1.Values = new object[] { guid.ToString() };

            FilterExpression _FilterExpression = new FilterExpression();
            _FilterExpression.FilterOperator = LogicalOperator.And;
            _FilterExpression.Conditions.Add(_ce1);
           

            _Query.Criteria = _FilterExpression;
            BusinessEntityCollection _Bec = service.RetrieveMultiple(_Query);

            email oEmail = null;

            if (_Bec.BusinessEntities.Count > 0)
            {
                oEmail = _Bec.BusinessEntities[0] as email;
             }

            return oEmail;
        }