GSX doesn't obviously have anything to do with it, since there's NO WAY a standard application ( =not a driver ) can cause a shut down of your system.
You are mislead thinking "it's GSX" ( because it seems not happening if you don't use it ) but that's just because, for some reason which can only be caused by either a driver problem or an hardware problem, which is only trigger because some of the objects/textures created by GSX, which of course are 100% correct, fine and proper, for some reason are showing a problem in your system, most likely related to video drivers, which are the most common cause of such hard crashes, even if they are surely not the only ones.
Also, I see you use overclocking, with a very powerful CPU with just 650W PSU, which I'd say it's a bit on the low side to do overclocking. Just the additional load caused by using an add-on like GSX, even if it's not much, might have been enough to trigger a power supply problem.
So, the first thing to try is:
- Stop overclocking.
- Download the latest version of your video drivers and do a clean installation of them, to remove any possible tweaks.
- If the system is more stable with no overclocking, consider getting a more powerful PSU and/or a better cooling system.
