PANIC: fatal region error detected; run recovery.

["Clemson, Chris \(IHG\)" <Chris.Clemson@ihg.com>]

I have encountered this error in our event log here.
I am using the cygwin version of OpenLDAP v2.3.39-1 with cygdb-4.5 on
Windows 2000
This has been working swimmingly for a couple of months now (although
restarts automatically every weekend for an import).
A user rang me to say that it wasn't working anymore, and Outlook was
complaining there was a MAPI error.
On further investigation, I saw several attempts to search in the event
log:

conn=1986 op=1 SRCH base="cn=wwwww,dc=XXXX,dc=YYYY,dc=ZZZZ" scope=0
deref=3 filter="(objectClass=*)".
conn=1986 op=1 SRCH attr=cn commonName mail roleOccupant display-name
displayname sn surname co organizationName o givenName legacyExchangeDN
objectClass uid mailNickname title company physicalDeliveryOfficeName
telephoneNumber.
bdb(dc=XXXX,dc=YYYY,dc=ZZZZ): PANIC: fatal region error detected; run
recovery.
conn=1986 op=1 SEARCH RESULT tag=101 err=80 nentries=0 text=internal
error.
conn=1986 op=2 UNBIND.
conn=1986 fd=25 closed.

from various users, (including myself when I was doing some
troubleshooting).
Restarting the service (without doing a "run recovery") has cleared this
problem.
It happened once before I had completely implemented it, but just put it
down to a one-off as I was doing a lot of changes.

It sounds like it's a database error rather than an OpenLDAP error as
such.
Has anyone else encountered this before and knows why it happens?

Thank you,

Chris