Kernel panic no init found after installing Saucy

[Colin Law]

I have installed from the Saucy 64 bit desktop daily image onto a
spare partition (sda3) on my PC and the install appeared to go without
problems.  However when I try to boot it I get a kernel panic - not
syncing: No init found.  Booting into 13.04 on the other partition is
still ok and from there I can see that that syslog does not exist so I
presume it is failing before it gets as far as starting loggin.  When
I boot into recovery mode I can see the terminal o/p before the
failure.  The lines immediately before the failure are:

Freeing unused kernel memory: 864k freed
Write protecting the kernel text: 6232k
Write protecting the kernel read-only data: 2500k
NX-protecting the kernel data 4008k
Failed to execute /init
Kernel panic - not syncing: No init found

I can see that initrd.img exists and is a link to
boot/initrd.img-3.10.0.6-generic which is 17.1MB

Hitting 'e' from grub I see
set root='hd0,msdos3'

I used the self check on the USB stick after burning the iso and it
said no errors were found in the files.

I have re-downloaded the image and re-installed with the same result.

There seem to be no such issues reported on launchpad.

Any suggestions on what might be the cause or how to debug the problem
would be appreciated.  I don't want to submit a bug till I am sure it
is not operator error.

Colin