U2713H Turns Black without a reason

Hi,

I have notice a strange thing with my new U2713H. Sometimes (like 3 times in a week) it has turned black without a reason. I use the computer and without a notice the U2713H goes black. Problems solves to turn off and On the screen (at least this time).  First time it happend the screen locked up and I have to turn out the electricity Cable. Is this something that someone more notice? I have RevA03 manufactor 2012 November. Nvidia Graphic Card 680. Also settings buttomes becomes like a freezing state sometimes (is not a crucial thing but anyway something to notice). The Power lamp still lights so its like a freezing Idle/sleep mode. I also have the latest driver to the graphic card. 320.49 is the driver i use. I use the DP In Contact at monitor.