C#, Qt, Qyoto - buttons work sometimes

Don't know if this is a Qyoto bug or I'm doing something wrong. When I build my project and click buttons sometimes they work, sometimes they don't. If I rebuild it, then they might start working or stop. Really strange.

I have these functions:

QObject.Connect(btnSource, Qt.SIGNAL("clicked()"), MainWindow, Qt.SLOT("GetSource(MainWindow)"));
QObject.Connect(btnAbout, Qt.SIGNAL("clicked()"), MainWindow, Qt.SLOT("ShowAbout(MainWindow)"));

[Q_SLOT]
private void ShowAbout(QMainWindow win) {
QMessageBox.About(win, "About", "About Project");
}

[Q_SLOT]
private void GetSource(QMainWindow win) {
fileDialog = new QFileDialog(win);
string folderPath = "";
folderPath = fileDialog.Directory().ToString();
}


The ShowAbout sometimes shows the message, sometimes it doesn't, the GetSource never works. What am I doing wrong? Thank you.