Many ATI owners suspect the driver isnt quite right. I get the flickering on the DP port but it will go away if I unplug it and plug it back in. It happens on the DVI ports intermittently. Are you using a DVI-dual cable? You didnt mention the size of your monitor. These are identified with all of the pins being present - a DVI single has two obvious sets of pins. If running at 1900x1280 you should use a DVI-dual cable.