Loader/installer problems - can't load 'kernel'

[Chris Carr]

I've tried to install FreeBSD 8.2 on two different Macs which both  
have bad optical drives. So I am trying to perform the install from  
removable media. I've tried USB flash drive and an external firewire  
HD. Neither is working. I can get the loader to boot (manually through  
open firmware) but I can never get past the loader. It always ends up  
saying "can't load 'kernel'."
When trying to boot installer from the USB drive I also get could not  
open <OF device tree path>,  a few times before it gives up with  
"can't load 'kernel'."
I followed the steps from this post: http://forums.freebsd.org/showthread.php?t=25266 
.
I can use dir <OF device tree path>,:\ to list the contents of the  
install CD on the flash drive. I've passed the argument of the <OF  
device tree path> to the loader when I run the boot command.

When I run lsdev, it shows no block devices available. Should I give  
up and set up a DHCP/TFTP/NFS server and run the install that way?  
Thanks for any help you can offer!

Thanks!
Chris