weird flickering lines on monitor

[plantation]

So today I upgraded my computer's power supply and bought a new video card. Ever since I installed the new power supply and video card, I've noticed flickering lines that are going diagonal on my monitor. Lowering the resolution gets rid of them, but I've been using the monitor's natural resolution of 1920x1080 for almost a year now. The problem just started today. Does anyone have any idea what this could be? Should I go back into the computer and try to mess with the power/video card or does this sound like a monitor problem?

[ice216]

What color are the lines?

[plantation]

Black/gray. They're really faint and show up better on brighter colors.

[Libram]

My new Asus VE228H monitor does the exact same thing. It's very faint and hardly noticeable unless I shift my eyes quickly across the screen.