Sylvia,
Yes, I went back into the BIOS and enabled Hyper Threading and am getting the same new shutdown errors and endless reboots at the login screen. I can login normally with Hyper Threading disabled in the BIOS and the fresh install of Windows 8.
I've since spoken with Victor of tech support this morning (Incident #5386093). Victor has suggested to RMA the board first, then trying to install Windows 8 again before doing an RMA for the processor.
Before I RMA the board, I may get another power supply and try installing with a new Power Supply?
Any advice you have is welcome Sylvia.
What puzzles me is it worked for six months with Hyper Threading enabled, now the system will not boot to the login screen, even with a fresh install of Windows 8 bare bones with one stick of RAM and a new hard drive on a different port.