Can't load kernel errors (with wierd bios messages)

[Scott Ullrich]

Hello list!

I'm trying to understand a problem that keeps coming up quite often
but I honestly have no idea what is going on.

In random cases after upgrading I'm seeing the message:
Can't work out which disk we are booting from.
Guessed BIOS device 0xffffffff not found by probes, defaulting to disk0:

can't load 'kernel'

Screen shot of the error in action:
http://www.pfsense.com/~sullrich/CantFindKernelError.JPG

Does anyone know what causes this error?  

Thanks in advance!

Scott