I went back to a single Athlon board and chip. Some fix. :(
I think it's the motherboard. Putting the board into single CPU mode and
recompiling the kernel that way, then removing the CPU helped none. Trying
yet another stick of memory got me nothing.
So now I'm getting the board replaced. Of course, I phone up ASUS and they
discontinued the board because it has too many problems. Bingo!