Child QWidget is not painted correctly

Question

I need to show a virtual keyboard when the user selects an input text field in a webpage. This code runs on an set top box.

I am extending the QWebView, which is creating a new keyboard widget as a child.

WebView::WebView(QWidget* parent = 0): QWebView(parent)
{
    WebPage *page = new WebPage(this);
    this->m_keyboard = new widgetKeyBoard(this, Qt::Window|Qt::CustomizeWindowHint);
    this->m_keyboard->createKeyboard();
    this->m_keyboard->hide();
    connect(this, SIGNAL(launchVirtualKB(WebView *) ), SLOT(launchKeyboard(WebView *)));
}

The widgetKeyBoard is made up of QGridLayout with many children QKeyPushButton.

When I do a show of keyboard, I see the whole keyboard drawn briefly and then overwritten 30% of the keyboard from the below web page (overwritten near the input field). I tried to have my own repaint for webview and mainwindow, but still see that someone else is overwriting.

What could be causing such an issue. I am using QT4.8.