Qt oddness within Unity

I've noticed some very strange behaviour when launching a Qt-based UI from Unity recently. Possibly from updating Qt, but the UI would fail to respond to mouse clicks or other signals, until I dragged or resized the window, at which point, all the inputs I had made would then replay very quickly and get up to date.
The only solution I've found is to create a QTimer outside of the main window context (the QApplication is its owner), and set it to call QCoreApplication::processEvents every 100ms or so.

QTimer *timer=new QTimer(pApp);
timer->setSingleShot(false);
timer->start(100);
CONNECT_AUTO(timer,SIGNAL(timeout()),w,SLOT(Idle()));