Problem with Hyundai L70S

I've had this monitor for about two years and it has been working fine until recently. When I turn the computer and monitor on, I get an image for a split second and then the screen goes black. After about 2 seconds, the image comes back for a split second and goes away again. This keeps repeating. Sometimes the problem goes away for a day or two and then for no apparent reason it comes back. I'm pretty sure it is the monitor's problem because I plugged in a different monitor and the problem's gone. Anybody have an idea what the problem is? Thanks in advance.