open directory error 14002

since i installed last week os x server 2.1.1 fresh and clean, i already had to roll back THREE times a time machine backup from some hours earlier.

because users were unable to mail or login.

server app sees no users at all anymore.

workgroup manager tells me 127.0.0.1 has unexpected error 14002.

why does this happen? am I the culprit or is it the system?

how can I, when it happens, restore the open directory database quickly and correctly?