Hi, I'm using a 2600K & the GA-Z68XP-UD3P under the UEFI version U1G, and I can disable CPU PLL Overvoltage under Advance CPU Core Features.
Also, try loading Optimized Defaults and then re-enter your OC settings, drive options, etc. and see if that helps with boot loops.
Honestly, there's still no clear answer to why boot loops happen, but it just seems to be a different issue for everyone.