from jon@cs.wits.ac.za:

this is my experience and summary of the cure:

This is about mkLinux failing to reboot after modifying the partitioning of
your mkLinux disk from the macos side.

i did this myself to my server (with a few hundred users) and had cardiac
arrest for about 10 minutes trying to grasp why it was no longer booting,
then i figured out by myself what i did wrong and reverted to the original
partitioning.

the error it reports, is being unable to find the root partition and config file; it mentions looking for something in /dev/sdxx/root/mach_servers/

and can't find it. The reason is, if you modify the partition map of the drive,
such that a new partition is inserted BEFORE the root, usr and swap partitions,
mkLinux will not boot because it can no longer find the partitions it is 
expecting.

For example, my partitions looked something