ur code seems fine.... and am also begining to scratch my head
need to know 2 things -
1) is CShoppingCartWidget::addEntry reached ?? put qDebug for tempOrder as u did for order. What values you get there ? As for breakpoints in constructor, try qDebug in constructor. Sometimes breakpoints cannot be reached due to some other reason.

2) how are u adding the tempOrder to the table ? bec the code till now looks fine. may be u are making mistake somewhere else.