I don't know if it's your case, but there's a known issue with windows vista (maybe seven) and Nvidia card on laptop.
When using intensivly GPU, card drivers crash. most of time Windows succesfuly recovers; sometimes you've got a blue screen.
It's because of nvlddmkm.sys. incompatibility with Windows
Seems there's no driver solution atm.
A mid solution is to downclock the core and memory GPU.
I tried on my laptop but no way, still crashing each time I try to launch a render.
For the moment I can't test Octane
My card is too old on my PC (7600) and my laptop crashes (9400; I know little bit old too said Radiance
)
I'll be back soon with test from work