He probado colocar EnforceConstraints = False y nada, no hay caso. En si las consultas que estoy realizando son del tipo "Select".
Verifiqué las claves, las relaciones entre tablas, ejecuté el store procedure desde la base y con la opción visualizar datos de VS2005 y en ambos casos me trae datos sin ningún problema.
Las paginas son dos (maestro-detalle) y el error ocurre cuando voy al detalle

Espero que alguno pueda darme alguna pista.
[ConstraintException: No se pudieron habilitar las restricciones. Una o varias filas contienen valores que infringen las restricciones NON-NULL, UNIQUE o FOREIGN-KEY.]
System.Data.DataTable.EnableConstraints() +1808933
System.Data.DataTable.set_EnforceConstraints(Boole an value) +39
System.Data.DataTable.EndLoadData() +138
System.Data.Common.DataAdapter.FillFromReader(Data Set dataset, DataTable datatable, String srcTable, DataReaderContainer dataReader, Int32 startRecord, Int32 maxRecords, DataColumn parentChapterColumn, Object parentChapterValue) +218
System.Data.Common.DataAdapter.Fill(DataTable[] dataTables, IDataReader dataReader, Int32 startRecord, Int32 maxRecords) +318
System.Data.Common.DbDataAdapter.FillInternal(Data Set dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +221
System.Data.Common.DbDataAdapter.Fill(DataTable[] dataTables, Int32 startRecord, Int32 maxRecords, IDbCommand command, CommandBehavior behavior) +162
System.Data.Common.DbDataAdapter.Fill(DataTable dataTable) +107
LeyesTableAdapters.LeyTableAdapter.GetDataBy1(Null able`1 CodPaClave) +253
LeyBLL.GetDataBy1(Int32 CodPaClave) +48
[TargetInvocationException: Se produjo una excepción en el destino de la invocación.]
System.RuntimeMethodHandle._InvokeMethodFast(Objec t target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) +0
System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) +72
System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) +358
System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) +29
System.Web.UI.WebControls.ObjectDataSourceView.Inv okeMethod(ObjectDataSourceMethod method, Boolean disposeInstance, Object& instance) +482
System.Web.UI.WebControls.ObjectDataSourceView.Exe cuteSelect(DataSourceSelectArguments arguments) +2040
System.Web.UI.WebControls.BaseDataList.GetData() +53
System.Web.UI.WebControls.DataList.CreateControlHi erarchy(Boolean useDataSource) +284
System.Web.UI.WebControls.BaseDataList.OnDataBindi ng(EventArgs e) +56
System.Web.UI.WebControls.BaseDataList.DataBind() +72
System.Web.UI.WebControls.BaseDataList.EnsureDataB ound() +55
System.Web.UI.WebControls.BaseDataList.CreateChild Controls() +63
System.Web.UI.Control.EnsureChildControls() +87
System.Web.UI.Control.PreRenderRecursiveInternal() +41
System.Web.UI.Control.PreRenderRecursiveInternal() +161
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1360