How to use Qt translations directly with QApplication:: tr()

In an application developed in Qt I have a non-visual class (i.e. that is not inherited from a QWidget) but that handles text strings that must be presented to the user. To use the QT translation engine, I set all strings using the QApplication::tr() function.

The strings are correctly displayed in the Linguist tool, under the context of QApplication (as expected - see image below). However, when I saw code I change the Locale of the application, only strings under the context of MainWindow are changed.

The code I use to change the language is as follows:

void MainWindow::setLocale(QString sLocale)
{
    QTranslator *pTranslator = m_mpTranslators[sLocale];
    if(pTranslator)
    {
        for(map<QString, QTranslator*>::iterator it = m_mpTranslators.begin(); it != m_mpTranslators.end(); ++it)
        {
            qApp->removeTranslator(it->second);
            QApplication::removeTranslator(it->second); // Essa linha não existia antes!
        }
        qApp->installTranslator(pTranslator);
        QApplication::installTranslator(pTranslator);  // Essa linha também não!

        if(sLocale == "pt_BR")
            m_pLocaleButton->menuAction()->setIcon(QIcon(":/resources/icons/pt_BR"));
        else
            m_pLocaleButton->menuAction()->setIcon(QIcon(":/resources/icons/en_UK"));

        ui->retranslateUi(this);
        updateUI();
    }
}

I think it is important to note that the change of the texts in the graphical interface is immediate (via calls of ui->retranslateUi(this) and updateUI()), but that the calls of the non-visual class occur later the exchange of locale, so the text should be translated correctly.

In the above code, I also came to include the lines marked with comments, but this did not cause the translation to accompany the locale set.

Does anyone have any idea where I might be making a mistake?

Edition:

Qt version is 5.1.0 (32 bit), and I'm running on Windows 7 (64 bit). Translators are created in the class constructor MainWindow, as follows:

// Setup the translation system
QTranslator *pPortuguese = new QTranslator(this);
QString sPortuguese = QCoreApplication::applicationFilePath().replace(".exe", "_pt_BR.qm");
if(pPortuguese->load(sPortuguese))
    m_mpTranslators.insert(map<QString, QTranslator*>::value_type(QString("pt_BR"), pPortuguese));
else
    qWarning() << "Portuguese translation file not found";

QTranslator *pEnglish = new QTranslator(this);
QString sEnglish = QCoreApplication::applicationFilePath().replace(".exe", "_en_UK.qm");
if(pEnglish->load(sEnglish))
    m_mpTranslators.insert(map<QString, QTranslator*>::value_type(QString("en_UK"), pEnglish));
else
    qWarning() << "English translation file not found";

The m_mpTranslators attribute is a simple map that relates the locale string to the translator: std::map<QString, QTranslator*> m_mpTranslators;