I have a Philips 234CL monitor with a GeForce GT 440 GPU. Ever since last week, at a refresh rate of 60 Hz, the monitor shows a bar of faint green lines that are somewhat spaced out, running across the upper part of the screen; the bar ends abruptly somewhere on the left part of the screen. They're also present when Windows boots up and when I disable the display adapter. At a refresh rate of 50 Hz, however, they're almost unnoticeable.
Is this a problem with the monitor or something else?