I got the PC to boot at stock with 4GB, then I got it to boot using the 30% OC profile, then I got it to boot with 410FSB but using the first memory divider for PC-4800 (I did read the other posts before asking and saw this might work, but I didn't know if I'd get anywhere on my own.)

So I've stopped screwing around since if I make the BIOS change back to 1:1 again and it fails to boot, I'll have to pull 2 sticks out just to reconfigure the BIOS then shove them back in again and go back to 3.12GB as reported by Windows. I'll see how it goes for now with 'slower' memory...