Debug QT4 Gui Application

[cae]

Hi, i created an empty project (it only has a mainwindow invoqued on main.cpp) but i'm not able to debug it, the code of the main.cpp looks like this:

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

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But it stops at the QApplication a(argc, argv); line.

And the message: Stopped: "signal-received"

But when i decide to build a release and run it, it works without any problem

Can any one help me?