I have a Gateway GZ7220 AIO and am having some issues with it, I don't think it's a hardware problem as I have just rebuilt the machine (New Motherboard, Video Card and Hard Drive) all the drivers are their most current and Windows Vista is fully updated on a (fairly) fresh install. Anyways at the moment when you go into certain windows they pulsate and also if you hit ctrl+alt+del the screen goes to the one where you choose task manager etc and pulsates black to regular and resets the position of the mouse to the center of the screen ever flash so you can't choose anything (they are pretty quick flashes/pulses) The computer was running fine yesterday for a bit after I updated the drivers and Catalyst control center, but at some point the screen went to a dark greyish and had colored horizontal lines all over it, performed a reset and it works fine aside from the pulses. Anyways I have never ran into something like this before and am at a loss as to what could cause the problem.
I can't say i've heard of such an issue, but you could try and roll back the Catalst driver. That might solve your problem.
This can be allot of things, power supply to a short somewhere on the motherboard... Does this happen when you are in the Bios ? OR when in safe mode ?