I have the same issue as those who posted here. I followed the diagnostic steps on page 44 and the fine horizontal lines are clearly visible in all modes except black and are much harder to see in blue (mostly because its darker). The lines are most prominent in the center of the display and fade away towards the edges. I've tinkered with all settings on the monitor with no improvement. Do I need to exchange this monitor through Dell or through the store where I purchased it?