The bug was introduced with the 2.0.1 release and is quite simple to reproduce. Create a new project with the Empty V-Play 2 Project template. Compile, run, press any key, look at the pretty assert window.
The GlobalKeyForwarder is reseting the QEvent accepted flag from true (set by Qt) to false.
Qt 5.3.0 source from the online installer.
the event is forwarded to a QQuickItem.
void QQuickItemPrivate::deliverKeyEvent(QKeyEvent *e)
Q_ASSERT(e->isAccepted()); // <– assert because isAccepted is no longer true.