drive image dd booting backup question

[trader]

Hi,

I have two identical (model/size/etc.) hard drives 
in a computer, both of which are recognized by the 
PC's BIOS, both of which are listed in dmesg as ad0 
and ad1, respectively, and both of which appear as 
/dev/ad0 and /dev/ad1.  One is master, one is slave.  
The slave (ad1) is never mounted.

My goal was to install FreeBSD and set up apps 
for a user on the 'master' drive (ad0), then 'image' 
the drive over to ad1 (to produce backup media for 
the project) using the following command:

dd if=/dev/ad0 of=/dev/ad1 bs=512

So far, so good, everything works great.  dd 
reports that everything went smoothly.  Then I 
attempt to boot off the that slave drive, after 
performing the following steps to make what was 
once ad1 is now the primary ad0 drive:

* disengaged the drive data cable from ad0
* set ad1's jumper to a single drive
* changed the bios to recognize only one drive

When I try to boot off what was once the slave 
drive (ad1), however, I get errors that /boot/loader 
and /kernel can't be found.

>> FreeBSD/i386 BOOT
Default: 0:ad(0,a)/kernel
boot:
Not ufs
No /kernel

Does anybody have any thoughts on what I might 
have missed?  Google and newsgroup searches have 
not produced an answer that's helpful.  Of course,
I hope I haven't committed some remedial error and 
wasted your time with this post.

Thanks,

G. Sherman