Waiting for RPC reply to 'destroyWidget' timed out

[Archa4]

I recieve this message when quitting my program (if the program has worked for less then 20 sec - no message):

Waiting for RPC reply to 'destroyWidget'' call timed out
Write error:  "Unknown error" 
Sending RPC id failed for call of 'setSymbianSoftKeys'

Waiting for RPC reply to 'destroyWidget'' call timed out
Write error:  "Unknown error" 
Sending RPC id failed for call of 'setSymbianSoftKeys'

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If I try to debug my program, then debugger stops working at a moment, when I play with items on layout:

void MainWindow::closeTaskMain()
{
    calendar->hoursList = dataManager->hoursList;
    taskMain->setParent(0);
    layout->addWidget(calendar);
}

void MainWindow::closeTaskMain()
{
    calendar->hoursList = dataManager->hoursList;
    taskMain->setParent(0);
    layout->addWidget(calendar);
}

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What can this problem be related to?