I have a LG Monitor (19M37A). When I start the computer, the signal goes off after some time. However the monitor power indicator remains on and the CPU also works fine. The signal comes automatically after some time, and then goes off again. I have replugged the cable which connects the monitor and the CPU, and also cleaned the RAM. I got the monitor in exchange of my under-warranty LCD monitor (its parts were no longer manufactured so I got a new monitor) and it seems that the company has given me a defective product. What could be the cause for this problem?