Hello!
I have a strange issue only happens when I use the display port, that sometimes when launching a game(only when launching a game), it will fail to show the content and the screen will just switch a black screen showing the display port message, I can still hear the background music but nothing is showing on the screen. Once I change output to HDMI, the screen shows the content. The display port cable used is CableMatters and the monitor is Samsung U28E590D

I've seen a few folks with somewhat similar issues with displayport cables. It turned out that they weren't using VESA displayport certified cables, and that was the problem as they weren't made properly.
 
That may or may not be the case with your displayport cable as well.

I'm using this cable Cable Matters Gold Plated DisplayPort to DisplayPort Cable 6 Feet - 4K Resolution Ready, purchased from Amazon 10 months ago, and was running fine with GTX 960 SC just fine during that time without a single issue.

Try different drivers, 373.06 has been the last all around good driver that Nvidia released without serious issues.
 
If that doesn't work, try a different display port on the monitor and GPU.
 
If you don't have a spare displayport cable to test then you might want to call EVGA to see about starting an RMA - http://www.evga.com/about/contactus/
 
Were I in this position, I'd try another displayport cable first because they've been known to go bad just like other cables. I've actually had an HDMI cable go bad due to stress on the connector.