zfsloader 9.0 BETA3 r225759 - i/o error - all block copies unavailable

Hello all,

I upgrade from 9.0-BETA2 to 9.0-BETA3 (r225759) and when booting from a 
zpool I get:

ZFS: i/o error - all block copies unavailable
can't open '/boot/menu.rc': no such file or directory.

I pxe boot mfsbsd 8.2-RELEASE + zfs v28

then:

mkdir /rpool
zpool import -R /rpool rpool
mount -t zfs rpool/boot /mnt
mv /mnt/boot/menu.rc /mnt/boot/Menu.rc
cp /mnt/boot/Menu.rc /mnt/boot/menu.rc
umount /mnt

shutdown -r now

and the next boot run smoothly...

PS.
I have to boot from pxe because after the i/o error, the kernel was 
booted but encounter a double fault. I try 5 times with the same result.

I think that on my configuration only the kernel without ACPI encouter 
this trap.

Henri