I have a Mac G5 with an Apple Cinema HD display. The video card is an ATI Radeon 9800. It is showing red and green dots that have trails when you move a box. The dots get bigger is you change the resolution to a smaller size. Anyone ever experience this and know of a solution. This computer has not always shown this behaviour. I am afraid it is either a bad video card or something I have added.
Sounds very video RAM to me, which suggest video card. If you boot from an installer CD, (Don't install the system), do you get the same problem, if so then it's most likey the video card, with a slim outside change it's the logic or CPU cards, but I would be very supprised if it was ether of those.