QTcpServer (FortuneServer) Example not working on Windows 7

The QTcpServer Fortune Server example isnt working on Windows 7. It doesnt bind itself to a valid port.

in server.cpp

tcpServer = new QTcpServer(this);
    if (!tcpServer->listen()) {
        QMessageBox::critical(.....);
        close();
        return;
    }
    statusLabel->setText(tr("The server is running on port %1.\n"
                            "Run the Fortune Client example now.")
                         .arg(tcpServer->serverPort()));

tcpServer->serverPort() returns 0, which means the server isnt listening for conenctions.
tcpServer->listen() is called without a port parameter. So it should choose a port automatically which it doesnt. The call however returns true

Under Windows XP the example works fine, starts up and automatically chooses a port.

Other Examples using QTcpServer in the same way, without specifying a port explicitly, are failing too.