You are not providing any system information or other details. From the screenshot we can conclude that it's Windows 8, but that's about it. In any case, start by reading this and otehr related articles on my site:
Windows 8 Pro 64-bit
Nvidia GE-force graphics card
Have tried deathorizing quitting other things that share nextowrk, restarting, and use of firewall.
I restarted before doing most of those things... It works upon another restart. Sorry for wasting your time.