Thanks for this hint!

I have an N9, and suddenly I got these 2 blue circles and for every action I needed to make a double touch instead of a simple touch.
(It happened while playing with x11vnc...)

The whole ergonomics has changed. Even after a reboot, the 2 circles were still there.

Thanks to your hint, I've found the solution: turn off the developer mode, then turn it back on.

Peter