When you add a new mesh, the overlay appears in the bottom left of the screen allowing you to change certain properties. Recently, however, when I try to click on any setting, the box disappears. I've tried clicking, dragging and any combination of both, but the overlay doesn't respond and vanishes as soon as you release the mouse button.
Obviously you only get one chance to change these properties - so I'm stuck without it.
Could an add-on be causing the problem?