I don't know if this is hardware or software related, so I kept it in this topic.
There is a constant horizontal stripe that takes up the second and third row of pixels from the bottom of my monitor. The color varies, but it seems to be some sort of an average color of the column above it. For example, if I move a black box around a white space (like in paint), I can see the stripe change to gray in the areas above which the box is (if that makes sense). If I widen the black box vertically, the color becomes darker.
The stripe does not show up on screenshot, so I took a picture with a camera to show it.
The stripe exists at all resolutions.
It is superimposed on everything -- including full screen applications and the taskbar.
It does not go away with a restart, sleep or hibernate, and I can't recall exactly when it showed up. I did recently install many Windows 7 updates, however, but no new video drivers.