My monitor sometimes flickers and it gives me headaches. It did not flicker with my old computer. My monitor is a Samsung 19" LE19R71B (1440 x 900, 75 Hz). It is a TV/PC monitor. Video card is Sapphire Radeon HD 4850 Dual slot fansink. Video card only has DVI output, i use an adaptor and a VGA cable. It does not flicker with my other 17" pc monitor (1280 x 1024, 60 Hz). Any suggestions?