cannot add DN b/c already exists, but it doesnt

["David Koopman" <dave@koopmancc.com>]

I am having a problem where my 90,000 entry openldap-2.0.25 compiled on a
RH 7.2 machine OS running db-4.1.24 on the backend.  I am using LDAP for
qmail-ldap - storing email user accounts in LDAP.

configured and installed ldap from source with only the --prefix=/var/ldap
option.

When I initially loaded ldap with data, I did so with a PHP script that
reads data from a SQL database and loads openLDAP.  This went very
smoothly, all 90,000 user's info loaded in about 1.5 hours!

Now, all day long, users can make changes to their account, at whim.  I get
about 100 account changes per hour -- so the LDAP database is constantly
being queried and updated.  User can change their password, change vacation
response, forwarding address, etc, etc.  For the most part everything is
working well, until...

About a week into the implementation, I look into my logs to see how things
are going and there are 32 dns that absolutely will not update.  When I say
update, I really mean add...  when a user makes a change, I delete their
old dn, then add it back in.  Some are brand new, some are dns that existed
before, but cannot be updated.  When I try to add the the user entry, ldap
reports it cannot add because DN already exists.  If I try to delete the
DN, ldap reports in cannot delete because DN does not exist.  This really
messes things up.  Interestingly enough, I can add the user's information
with a slightly different DN and it works fine.  So, I have a handful of
DNs, 34 out of 90000, that I cannot use.  This is a problem for me because
I use PHP to automate the user initiated changes...  the DNs I use have
specific meaning.

Has anyone seen anything like this?  What is the solution?  I have another
machine that I am trying to duplicate the error on and I cannot.  On the
other machine, I thought I had built it the same (same software) to the
best of my knowledge.  I am running a script on it for 2 weeks now, non-
stop, where I have a set of ~90,000 users in a SQL database...  I cyclce
through all 90,000 in a loop...  for each user, I first delete their
existing DN, then I create their DN with their information (very similar
behavior to my production machine).  Like I said, this has been running for
2 weeks straight, non-stop updates, and I have not had one single error.
This is really baffling me.

Dave.