I've just bought a PowerBook G4 (black keyboard) second hand with a display problem. What it is, is sometimes strange rectangular grids appear around objects and eventually take over the whole screen. At first, it is a rectangle made up of couloured pixels next to the mouse and the the problem gets worse when the screen changes (open a program, hover over an icon in the Dock etc.) and then the whole screen is affected (i.e. it is difficult to do anything), leaving me with no choice but to turn it off. Any Ideas? Do you think it is a loose connection that is easily repaired?