typed Dataset Contrain Exception

Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints. Unfortunatly, there is no hint which Constraint(s) causes the exeption => try 1) set Allwo DBNull to true 2) Length of String ok ? (Set to max) 3) double key ? or try to load same rowset into a untyped dataset and copy each row and each field into the typed one