The focus keeps moving from the active window to nowhere in particular. Most annoying when I am typing as I have to watch the keys not the screen, not being a touch-typist. When I do look at the screen I can find that half of what I have typed is not there and has to be reentered. The window is still uppermost but not active.
This can happen even if I only have the one window open; and not just when I am typing.
Any ideas as to what causes it and how to fix it?