Flashing screen??

As some of you know I haven't been on here in a while (due to health problems) but when I was able to get back to the computer (Gateway, Windows ME, AOL 9.0) I noticed that I can just be typing away and or just trying to read something and the screen just flashes. Nothing freezes up or anything just small quick flashes.

Its usually the web page that flashes, and my AOL homepage in the back ground stays the same. You know like right now, this DG page is slightly smaller than my AOL homepage/toolbars and etc. But the DG page it the only thing that flashes.

Any clue as to what the problem might be??
My memory isn't low,so that can't be it.
I've done a disk clean up recently, done a disk refrag also.
I've ran a virus check (done weekly)

Any help?? Any ideas????

Thanks in advance for any help or advise you might have.