I ran apt-get update and apt-get upgrade this morning on an old server
(Debian Squeeze) and the system won't boot now. I get the error

kernel panic not syncing: VFS: unable to mount root fs on unknown
-block(0,0)

One of the updates was to kernel 2.6.32-5-686. I can boot in to safe mode
with this kernel, and the upgrade wiped out the older version of the kernel.

I have googled for possible solutions, but nothing helpful is popping up. I
am also running grub, and not grub2, but that is OK for this kernel
according to debian.org.

Any suggestions on how to proceed?

Thanks!

Mark