This started happening around Version 17. Running Windows 7. When the screen "jerks" the window moves up 1 line over the title bar and then goes back down. It seems to get worse when more tabs are open, and longer the program is running. It also doesn't accept text when th jerk ocurs ( I just quit correcting errors and see what happens.I don't see any abnormal activity coincident with the jerks on TaskManager or ResourceManager. These can happen several times a minute--I've had perhaps 20-30 while typing this sentence. They don't happen just when typing, however.