QSystemTrayIcon is not always showing on X11

Trayicon sometimes is not showing (actually it is visible, but it appear on top-left screen corner instead of tray panel ).

I found this problem on Kubuntu. But my friend confirmed it also on Xubuntu. You need to re-run application even twenty times because on my maschine trayicon doesn't appear on every ~7 application run. I have stable Qt 5.1 Mingw 64bit and this simply code:

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);

QIcon ico(":/22/player_play.png");
mTray = new QSystemTrayIcon(ico, this);

mTray->show();
}

This is totally random. While application starting, I see that tray panel is preparing space for my icon but finally this space disappear and icon is placed on top-left screen corner