A couple other things I've discovered while experimenting.
Like I said before, it does restart, however it hangs for about 10 seconds (much longer than it did last week) on the Shutting Down screen.
I took out the GPU, and I found out that its actually sitting on the Shutting Down screen forever.. I guess this may not be a motherboard problem after all. However, it still doesn't shut down even in safe mode, so I'm not sure.