Qt application with QSqlDatabase does not work properly when building it with macdeployqt

In my application I am using a QSqlDatabase to store some information. I did built it successfully with the following command (no errors even with verbose=3):

macdeployqt AppName.app/ -dmg -qmldir=~/dev/AppName/qml

Before that I successfully installed mysql55 using port

sudo port install mysql55

If I try to run my application it does not crash, but it also does not anything which involves database access.

This is my code for opening a database etc:

#include <QSqlQuery>
#include <QSqlDriver>

const QString DATABASE_NAME = "com.company.program.db";

MyClass::MyClass(QObject *parent) : QObject(parent) {
    mDB = QSqlDatabase::addDatabase("QSQLITE");

    #ifdef Q_OS_LINUX
    QString path(QDir::home().path());
    path.append(QDir::separator()).append(DATABASE_NAME);
    path = QDir::toNativeSeparators(path);
    mDB.setDatabaseName(path);           // NOTE: We have to store database file into user home folder in Linux
    #else
    mDB.setDatabaseName(DATABASE_NAME);  // NOTE: File exists in the application private folder, in Symbian Qt implementation
    #endif

    bool notOpened = !mDB.open();

    QMessageBox::critical(0, "MyClass", mDB.lastError().databaseText()); // always is 'out of memory'

    if (notOpened) emit failedToOpen();
    else {
        // some initialization
    }
}

MyClass::~MyClass() {
    mDB.close();
}

Has anyone experienced the same issues / a fix for this one?

Note: I am using Mac OS X 10.9 and Qt5.3.2

I managed to fix the out of memory error by executing this code:

#ifdef Q_OS_MAC
    QString databaseName = QApplication::applicationDirPath().append("/").append(DATABASE_NAME);
    mDB.setDatabaseName(databaseName);
#endif