'Connection' entity doesn't contain attribute with Name = 'ConnectionId'.

Ms Dynamics CRM 2011 - rollup 8

the following code produces this error during execution of the the last line in the code example

any ideas?

                QueryExpression Qry = new QueryExpression("connection")
                {
                    ColumnSet = new ColumnSet("ConnectionId"),
                    Distinct = true,
                    Criteria = new FilterExpression(LogicalOperator.And)
                    {
                        Conditions =
                        {
                            new ConditionExpression("record1id", ConditionOperator.Equal, fCrmEntityInstance.Id),
                            new ConditionExpression("record2id", ConditionOperator.Equal, RelatedEntityId),
                            new ConditionExpression("statecode", ConditionOperator.Equal, 0)
                        }
                    }
                };

                EntityCollection coll = fOrgService.RetrieveMultiple(Qry);