I have a 17 inch 1.67 GHz powerbook and a 23 inch ACD. Im having this strange problem where if I use my powerbook in dual screen mode, then the image on the ACD is jittery. It is hard to explain, take this as an example: If you have a vertical black line on a white background, then sometimes individual pixels of the black line will shift suddenly to the right or left one or two pixels. It happens very quickly, but is very distracting if you are trying to read black text on a white background. It is constant once is starts happening, its not like it just happens once in a while if an area of the screen starts to jitter like this, it will continue to do so until I close the lid of my powerbook. The problem also seems to get worse over time for example, when I first bring my powerbook out of sleep, then it is not noticeable, but after 20 minutes it is happening enough that it is hard to read without getting a headache. The interesting thing is that this does not happen on the ACD if it is connected to any other source, and it wont even happen on the powerbook if I close the lid and just use the external monitor. I also have not been able to notice this when the powerbook is used dual screen with any other display in my home, although I dont have any other displays nearly as high resolution as the ACD. Does anyone have any ideas of what might be the problem? Thanks j.