It means that the business object is trying to save a record that has been saved by someone else recently. It's used for detecting concurrency issues (when userA and userB both check out a record and modify it and they both try to save it at the same time). So, that's normal in a networked application scenario, but if it's happening all the time on one of your business objects, then the UpdateConcurrencyType might need to be changed to Off or OptimisticRowVersion if it's set on OptimisticAllFields. The exception being throw contains properties that show the row causing the data collision.