My Dell 2209WA now shows an irregular dark shadow on parts of the screen - but, only if the color(s) being displayed is not a primary colour. So for example, if I view a JPEG consisting of a single primary colour (white, red 255/0/0, blue 0/0/255, green 0/255/0, etc) I don't see the shadow. But change that green to one slightly mixed with red, etc, and the shadow shows up). Any idea from that what the cause is and how to resolve it? P.