Manipulating data with QSqlRelationalTableModel and QTableView

Hello,
I'm using QSqlRelationalTableModel and QTableView to access a sqlite database :

Code:

.....   sentenceModel = new QSqlRelationalTableModel(this);
    sentenceModel->setTable("sentence");
    sentenceModel->setRelation(Sentence_ActionId,
                         QSqlRelation("action", "id", "text"));
	sentenceModel->setRelation(Sentence_CharacterId,
                         QSqlRelation("character", "id", "text"));
    sentenceModel->setSort(Sentence_Text, Qt::AscendingOrder);
    sentenceModel->setHeaderData(Sentence_Text, Qt::Horizontal, tr("Text"));
	sentenceModel->setHeaderData(Sentence_Sound, Qt::Horizontal, tr("Sound"));
	sentenceModel->setHeaderData(Sentence_Language, Qt::Horizontal, tr("Language"));
    sentenceModel->setHeaderData(Sentence_ActionId, Qt::Horizontal, tr("Action"));
	sentenceModel->setHeaderData(Sentence_CharacterId, Qt::Horizontal, tr("Character"));
    sentenceModel->select();
 
    sentenceTableView = new QTableView;
    sentenceTableView->setModel(sentenceModel);
    sentenceTableView->setItemDelegate(new QSqlRelationalDelegate(this));
    sentenceTableView->setSelectionMode(QAbstractItemView::SingleSelection);
	sentenceTableView->setSelectionBehavior(QAbstractItemView::SelectRows);
    sentenceTableView->setColumnHidden(Sentence_Id, true);
    sentenceTableView->resizeColumnsToContents(); .....

and when i try to add a new record :

Code:

void MainWidget::addSentence()
{
    int row = 0;
    if (sentenceTableView->currentIndex().isValid())
        row = sentenceTableView->currentIndex().row();
 
    sentenceModel->insertRow(row);
    QModelIndex index = sentenceModel->index(row, Sentence_Text);
    sentenceTableView->setCurrentIndex(index);
    sentenceTableView->edit(index);
}

i receive the error:

ASSERT: "idx >= 0 && idx < s" in file c:\iwmake\build_vs2005_commercial_________________ padding_________________\include\qtcore\../../src/corelib/tools/qvarlengtharray.h, line 78

Any help would be appreciated.
Thanks,
Palma