I get the same problem. It seems to only happen once just after I have turned on my computer.
I have monitored temperatures of CPU’s and GPU and there is nothing out of the ordinary. Graphics settings are on lowest and framerate is a healthy ~100fps, but after a minute of gameplay (or just standing in LA) the PC normally then performs a Hard Reset. Please note this is not a crash.
I have attempted to update drivers but as per F-ing usual the so-called Nvidia Installer ALWAYS fails on one component.
I have however had one BSOD during the game, which I have never had on this system before.
i5 Quad core
Geforce GTX460
12gb RAM DDR3
I notice that others with the GTX460 are having the same problem, i wonder if this is purely a generational thing or whether there is some massive conflict between GW2 and the drivers?