We had similar problems and as a temporary measure returned to ldbm,
Interestingly, ldbm seems to use some of the same libraries but since we
reverted we have not had a single problem. If you do not really need the
transaction capability of Berkeley this may be an option for you.
In the end we decided that openLDAP is not really suitable for
mission-critical apps and have since made the decision to go to Novell
e-directory. You might like to look at that because although it is
commercial, it is not terribly expensive and blows the socks off
openLDAP.