that kind of thing used to happen to me on Bnet my PC would totally freeze until I upgraded my ISP mind you that was a few years ago.
maybe try the Unigine "Heaven DX11 Benchmark 2.5" and see what happens"
Or maybe try different drivers from
http://www.guru3d.com/news/nvidia-ge...iver-download/
I have heard of others having problems with the D3 game