I've had some weird graphical issues which lead me to suspect my graphics card (http://www.newegg.com/Product/Product.aspx?Item=N82E16814150617) is the culprit. I recently had both screens have fullscreen problems, one was a solid color, the other was vertical bars, one is HDMI the other is DVI so I assume that's the difference there.
A while ago I had an issue where I had lines that seemed 'burned in' to the screen from playing a game that didn't change screens (a card game) at what I think was the wrong resolution. The lines stayed in the monitor for a while until I turned them off and eventually they went away.
I've also had very small glitches or flickers for only a moment playing games that were very nice otherwise. (FC3, Skyrim) this issue was not at all constant.