Sheevaplug running Debian won't boot after initial "apt-get dist-upgrade"

[John Winters <john@sinodun.org.uk>]

I've successfully installed Debian Lenny onto an SD card in my new 
SheevaPlug and it booted fine.  I then followed Martin's instructions 
for fine detail adjustments (renaming the host, adding ntp, "apt-get 
dist-upgrade" etc.) before attempting to re-boot.  I did one extra 
thing, which was to edit /etc/fstab to reflect where my / partition was 
- on the MMC card.  Without that the "apt-get dist-upgrade" failed.  I 
then finished off the upgrade and re-booted.

It now gets as far trying to boot and says:

## Booting image at 00400000 ...
Bad Magic Number

and returns me to the monitor prompt.

As part of the apt-get dist-upgrade I noticed that the kernel went from 
2.6.29 to 2.6.30.  Is there an extra step needed to get the new kernel 
properly installed?

TIA,
John