Its more likely the junk PSU. Trying to overclock with that PSU is a bit pointless mate. It probably cant cope with the stress of the overclocked cpu AND graphics card running at the same time.
Also, set your overclock back to what it was, boot to windows, open cpuz, check the pci-e link width. If it says 1x, go back to the bios, and up the pci-e frequency from auto to 110, boot to windows, and check again with cpuz, it chould have changed back to 16x. You can either check for stability using the 110 setting, or restart and chage it back to auto.