I've discovered a bug with QWidget::restoreGeometry: if the restored geometry includes WindowMaximized and the window being restored to is already maximized, then the window gets resized to a non-maximized size, but behaves as if it was maximized (i.e. unable to resize the window; maximized window button appears as maximized).

I've included a small example that demonstrates the problem. When you run it you will have two top-level windows - maximise the one labelled "Test Window" by pressing the window maximize button in the title bar (or double clicking the title), then on the one titled Control Panel, press Save Geometry followed by Restore Geometry. You will now find that the Test Window is back to it's original size, but is un-resizable.

This example worked in version 4.4.3.