I have exact the same problem as Vic Bond.6549. I can not describe it more better than he have.
I use graphic card Gainward 660ti with win7 64bit and my problem seems to start when set graphic in gw2 to best apearence.
My problem is reproducable every time I go to Lion’s Arch. Probably the most graphic demanding area in the game. My screen got blank and memory clock drops to 324MHz. It can also happen in other areas but not so frequent.
I have no other problem then in gw2. I can can run graphic card stress test like Furmark or 3DMark 11 and there is no problem with graphic card.
In Furmark test my card temeperature goes to 85 degrees in 15 min and power usage is 120% and still my card work perfect, until I run GW2.