I have a almost 5 years old 24 inch cinema display. The display will show a dark smear vertical line/smudge on the left side when the display warms up. The smudge is not there when the display is cold, i.e. when I first turn on the display, the smudge is not there. But it will show up when the display is warm. If I turn off the display for a while, it disappear. The smudge is most visible in a green or grey(like when you turn on the computer) background. I cannot see it in blue or red or white or black background. The smudge is very similar to the one here: http://dustypayne.com/monitor.jpg But mine are not that obvious and is more straight. I have cleaned both the outside and inside of the glass panel and make sure it is not dust on either side of the glass. Anybody has idea what could be the cause?