laptop screen issue--anyone know?

So, my Acer Aspire 4520 is about 2 years old Other than one issue, it works still works great. The issue is very recent, and here's what happens. The computer screen will be functioning normally, and then suddenly, part of the screen will turn almost black. You can still read what it is displayed, but the part of the screen that is black will sort of flicker (it doesn't really flicker, but it's hard to discribe other than fading in and out). It will stay that way for a few seconds and then go back to normal. Has anyone seen or heard of a computer screen doing that? What can be done about it? Is my 2 year old computer on the blink?