Honestly, no idea what happened to it.
I uninstalled F@H, then reinstalled with the new SMP client. It's been going most of the day yesterday, and all of lastnight, and no problems. It's currently at 78%.
So I guess that fixed it? IDK. I turned down my v-core a touch the other day, temps were getting a bit high. I turned it up again lastnight, so maybe that was it also..