distortion or artifact in jpg image on screen

While editing some, but not all jpg images in PS Elements, there are flashing lines - a distortion in the image.  It does not affect the saved jpg but is annoying while editing.  Here's a screen shot of it.  The jpg is a shot of the bar code on the back of a book and the unwanted artifact appears on the upper two thirds of the image and is flashing on and off.  Anyone know what causes this and how to end it?