rootvp won't boot

[a-hobbs at sbcglobal.net]

>During the boot process, if I press the spacebar to abort loading of the
>kernel, I can do an ls and see the files on the drive. As soon as the kernel
>tries to mount root , I get this:
>
>Mounting root from ufs:/dev/da0s1a
>no such device 'da'
>setrootbyname failed
>ffs_mountroot: can't find rootvp
>Root mount failed: 6
>
>Any ideas?