Monitor problem: screen goes black, then comes in scrambled

I've had an Aquaview 9LS View & View monitor for almost 4 years (I use Mac OS X 10.3.9). Since tonight (about 1.5 hours ago as I type this), my monitor has been going black (even though the screen is on), then the image comes back again, flickering. There's this weird small cranking noise coming from inside the monitor (which reminds me of a light bulb), and the signal looks scrambled, as if there's a loose cable, or a dim bulb, or something. I've checked all my connections (though I didn't unplug anything), and they all seem to be sturdy. If the screen goes completely black for more than 30 seconds, I just turn the monitor off, then back on, which solves the problem until it happens again (usually 30-60 minutes later). How long do these monitors usually last? Is it possible that I might need a replacement?