Apple has been accused of attempting to cover up a persistent hardware problem with its PowerBook G4 notebooks, in which screen quality degrades. The problem, known as the "Vertical Lines" display defect, apparently stems from a manufacturing and/or design defect, whereby a cable grip is causing the display cable to fray. However Apple is reportedly deleting posts related to the issue on its support forum.
The problem begins with 1-pixel wide strips of unchanging vertical lines streaking the G4's display; this continues to proliferate across the screen, and other visual problems have been reported. Some users have had their display fixed, either under Apple's extended warranty or at their own cost, but because the cable grip defect has not been addressed their replacement panel subsequently fails.
Poor communication between Apple's service centers is being partly blamed for the company's slow response to the problem. Individual geographic areas maintain their own records, which are not necessarily shared with other centers: this reduces Apple's ability to monitor persistent or widespread failures. Those affected by the failure can find more detail here.