Many models of Samsung monitors have found to have problems after they have been used for a year or two. Just a few of the models are 910N, 710N, 713N. The particular behavior is that there is no picture and there is a floating menu that states: "Not optimum mode, Recommended resolution 1280 X 1024 @ 60Hz."
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Carefully open up the monitor with a knife to pry open the plastic tabs to get access to the interface board that has the video controller.
Look for the Novatek IC. Pins 5 and 6 need to have a 47-ohm resistor soldered between these two pins. The IC chip is a surface mount device type, so it will be a little difficult to solder. Another option is to put a 50-ohm SMD resistor between these pins.
Once this resistor is soldered, the monitor will function like new. Reassemble the monitor and plug in to test.