So, I got it to boot by setting CONFIG_AP_CODE_IN_CAR to off. That way the APs don't stumble over one another, and the machine boots just fine.
Here's the boot log:
http://ward.vandewege.net/coreboot/h8dme/minicom-20090624g.cap
You'll see a couple garbled lines, but I think that's just each of the APs saying they are ready.
I'm glad it works, but it still looks broken to me. Those lines look like ... TrainDQS RdWrPos1: ... in there.
Myles