I also got an issue where I would get sound from the game client, but it was giving me a black screen and was not responding.
nVidia GT 630
Intle i5 2500
8GB DDR3 1333 ram
2 GB DDR3 Dedicated video ram
In order to fix this, I rolled my driver for my nVidia GT 630 back one update to the second newest driver and that seemed to get Guild Wars 2 working again