I'm certain I used to be able to arbitrarily move any of the four sides of a selection without the other sides changing, but I can't anymore. When I click inside the selection and get the sizing bars displayed, when I use (e.g.) the bottom sizing bar to move the bottom edge, the top one moves also!
Likewise, I used to be able to pick up a corner and move it, but now the opposite corner moves as well.
I don't know whether I have accidentally changed a setting, but whatever it is, it's not nearly as useful anymore.
