ChangeConflictException: Row not found or changed

Hummm, I love this unclear exception message. I just can't believe there is not a condition somewhere to return whether the row was not found or just changed. It would be a lot easier to diagnose problems.

Anyway, after reading several article on concurrency regarding Linq to SQL and making sure the date field was sent correctly (like suggested everywhere), I finally pin-pointed the problem when I remembered that I had changed a NOT NULL column to a NULL column. Et voila. Problem solved!