Photoshop Problem

[JK_Photo]

Anybody else using photoshop ever have a problem like this when working with layers?
They are little artefacts of colour that appear and disappear when I move a pic on a layer. They will also appear randomly when I flatten an image. Bugs the p**s out of me!
sometimes they print(most of time) sometimes not. They can even show up in a grayscale image.