I'd start by upgrading to a modern, supported version of OpenLDAP.
That might not be enough, since back-sql sees little support, but it's particolarly true in this case, since back-sql was sort of heavily reworked and redesigned especially in order to make "obvious" things work (like loading from scratch) which was impossible earlier. In 2.3's source tree you'll also find some non-trivial back-sql database generation examples (for postgres, look into servers/slapd/back-sql/rdbms_depend/pgsql/).
Yes, i was trying using the sql-create-scripts from the current versions of OpenLDAP. That was not such a good idea since they are different.
Make sure you read the back-sql related FAQ instead of Howto's: all I could find on the 'net are at least terribly outdated, if not completely wrong.
OK, i will, Axel