New Samsung 2243BWX, colors get darker as you move up the screen?!?

I have a new Samsung 2243BWX, and strangely there appears to be a color gradient that darkens as you move from the bottom to the top of the screen.

I test this by dragging windows from the bottom to the top.

I was using an old NVidia GeForce MX420 analog output card with powerstrip, and I thought that the analog connection was causing this problem so I bought a video card with DVI out that supports 1680x1050 (monitor's native resolution). The card I got is MSI NX6200AX TD256 (Nvidia Geforce 6200 chipset).

To my dismay, the color gradient is still there, even with the new DVI video card!

I can make the effect less noticeable by adjusting the monitor's settings, but this is only masking the problem right? The monitor settings adjust every pixel on the screen, not a gradient from bottom to top, right?