boot problems with if=virtio

I know there have been a couple other threads here about booting with if=virtio, but I think this might be a different problem, not sure:

I am using kvm.git (41b76d8d0487c26d6d4d3fe53c1ff59b3236f096) and qemu-kvm.git (8f7a30dbc40a1d4c09275566f9ed9647ed1ee50f) and linux 2.6.20-rc3

It appears to build fine. I am trying to run the following command:

name=newcastle-xmailt01 dev1=/dev/disk/by-id/scsi-3600a0b80000f1eb10000069748d8c230 dev2=/dev/disk/by-id/scsi-3600a0b80000f1eb1000006dc48f45432 macaddr=00:50:56:00:00:06
tap=tap6
cpus=1
mem=1024
/usr/local/bin/qemu-system-x86_64 -name $name\
-drive file=$dev1,if=virtio,boot=on,cache=none\
-drive file=$dev2,if=virtio,boot=off,cache=none\
-m $mem -net nic,model=virtio,vlan=0,macaddr=$macaddr\
-net tap,vlan=0,ifname=$tap,script=/etc/qemu-ifup -vnc 127.0.0.1:6
-smp $cpus -daemonize

...and I get "Boot failed: could not read the boot disk"

This did work with the kvm-userspace.git (kvm-85rc6). I can get this to work with a windows vm, using ide. Was there a recent change to the -drive options that I am missing?

Thanks,

-Andrew