Reduce the Product Pop demo button to invisibility if a connection could not be made with the Product Pop server. There's a thin line going across the computer screen about a third of the way down, and a second one about two-thirds of the way down my monitor. This is entirely normal with these monitors.
Chances are, the monitor is fine.
There are a couple of factors that may be contributing to this flickering at high resolutions. First, your video card must specifically support the resolution setting. Second, your video card's vertical refresh rate usually decreases as the resolution setting increases. Most people find that resolution settings below 70Hz produce noticeable flicker. For maximum comfort, refresh rates of 72-78Hz are usually sufficient, but some users prefer even higher refresh rates.