From time to time, and in several different computers running various versions of Ubuntu, I've had Mathematica tooltips get "stuck", and persist on the screen even when I navigate away to other windows, which can be very disruptive:
The tooltip appears in front of all other windows, except new tooltips, and it interrupts things like middle-wheel scroll. This normally goes away if I quit and restart the front-end, but of course that can be pretty inconvenient.
Is this behaviour known? Is there a simple way to kill the Front End's tooltips without killing the session?