I have had a PC that everytime a BIOS setting was changed the PC would not POST, it actually turned out that the PC would not Hot boot. If I turned the Power off on the PSU switch and turned the PC back on, it worked fine. Problem turned out to be the RAM, it tests 100% OK with about 30 hours memtest, swapped to different brand and worked fine. This problem also didn't occur with 2 sticks, only 4.