yes it is the video card, when the GPU on the video card fails or dies, the moniter goes black for a sec, video card resets itself and the resolution goes with it.
You can just google that info. But for the most part a 128MB video card should do youjust fine. A buddy from work i help just got a ATI 9800 256MB for about $150. So really you can get just about any 128Mb or 256Mb viedo card as long as it is something you want and like. Most people will say that ATI\nVidia stink. It is all personal preference. I have both and love both. ATi in my older machine and nVidia in my newer machine. It just comes down to what you want.