Yeah, well. I have to reset the cmos battery before EVERY bootup, or else the GPU fans wont spin, and the screen will remain black. I can live with that, but when Im trying to install windows, it requires a reboot. So I have to turn it completely off. When im trying to get back where I was, i get a black screen.
I'm guessing your problem is caused by the CPU having to work harder when you reboot the PC as it has to load up all the previous data and this causes it to use more power while the Gfx card is still using a bit of power and the PSU can't power them both anymore.