There is a workaround described in the forum (Re: ZFS issues? kernel: KLD zfs.ko: depends on opensolaris-not a)
I've tested this workaround, and it works... until the reboot :-(
After the reboot the zpool is gone and you have to import it again, or export it 'before' you want to reboot your NAS.
I'm really looking forward for a new build...