panic at mounroot

["Justin C. Sherrill" <justin@xxxxxxxxxxxxxxxxxx>]

I installed to a second drive (ad1) in a system tonight.  Everything
went normally, and I used 'boot0cfg -B -b /boot/boot0 ad0' to install a
boot menu. 

On rebooting, the boot gets all the way to the point where it sees
disks, and then can't find the disk from which to mount the hernel.  I
get the mountroot> prompt, but specifying ufs:/dev/ad1s1a doesn't work
for locating the kernel.  Having repeated this several times, I found
that mountroot will panic at what seems to be random times - sometimes
right away after a bunch of times slapping return, or later.  

Here's what I get: 
mountroot>
panic: Root mount failed, startup aborted
panic(c04b95f0,c0485fd8,5ef000,c05e4d84,c028d901) at panic+0x84
panic(c0447ea0,c04b95f0,c0485fd8,c05e4d98,c0245608) at panic+0x84
vfs_mountroot(0,5e1c00,5ef000,0,c0137d3c) at vfs_mountroot+0xa1
mi_startup(5e1000,ff800000,c04f912c,c05e4c08,c05e4bf8) at mi_startup+0x90 
begin() at begin+0x43
Debugger("panic")
Stopped at Debugger+0x34:   movb     $0,in_Debugger.342

Ooh, looking at hexidecimal makes me sleepy.  The LiveCD boots fine, so
I'm suspicious of my older drive that's sitting there as ad1, but not
that sure.