mdadm segfaults - failed upgrade to Lenny - drops to busybox/initramfs

["Andrew M.A. Cater" <amacater@galactic.demon.co.uk>]

Subject should say it all. Updated a box to Lenny from Etch - boot on 
one partition, root and everything else on an mdadm managed raid5.

Booting now drops you to initramfs - attempts to use mdadm fail with a 
segfault. Have used a Knoppix which establishes that there is still a 
boot partition. Now downloading grml to see whether that will help.

HELP HELP HELP required - I've some important emails and some photos on 
there I'd like to recover. Relative novice with mdadm - I've just 
installed it a few times using the Debian installer and not really 
played with it from the command line.

Guide for idiots required, then, all help gratefully received.

Many thanks in advance,

Andy