Nullable Property Causes Errors When Null in NHibernate

<property name="OwnerId" column="OwnerID" type="System.Int32" not-null="false" />

[SqlException (0x80131904): Column name 'ModuleAnchorID' appears more than once in the result column list.]
   System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) +925466
   System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +800118
   System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +186
   System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +1932
   System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) +149
   System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) +1005
   System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) +132
   System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe) +149
   System.Data.SqlClient.SqlCommand.ExecuteNonQuery() +135
   NHibernate.Impl.NonBatchingBatcher.AddToBatch(IExpectation expectation) +35
   NHibernate.Persister.Entity.AbstractEntityPersister.Update(Object id, Object[] fields, Object[] oldFields, Boolean[] includeProperty, Int32 j, Object oldVersion, Object obj, SqlCommandInfo sql, ISessionImplementor session) +1055

[PropertyValueException: not-null property references a null or transient value:]
   NHibernate.Impl.SessionImpl.CheckNullability(Object[] values, IEntityPersister persister, Boolean isUpdate) +224
   NHibernate.Impl.SessionImpl.FlushEntity(Object obj, EntityEntry entry) +1019
   NHibernate.Impl.SessionImpl.FlushEntities() +182
   NHibernate.Impl.SessionImpl.FlushEverything() +90
   NHibernate.Impl.SessionImpl.AutoFlushIfRequired(ISet querySpaces) +64
   NHibernate.Impl.SessionImpl.Find(CriteriaImpl criteria, IList results) +217
   NHibernate.Impl.SessionImpl.Find(CriteriaImpl criteria) +42
   NHibernate.Impl.CriteriaImpl.List() +29