If you get any strange errors like "Invalid syntax" or "Invalid DN syntax" please check if your LDAP schema matches LAM's requirements.
Schema test:
This can be done by running "Tools" -> "Tests" -> "Schema test" inside LAM.
If there are any object classes or attributes missing you will get a notice. See LDAP schema files for a list of used schemas. You may also want to deactive unused modules in your LAM server profile (tab "Modules").
Logging:
If your schema is correct you can turn on LDAP logging to get more detailed error messages from your LDAP server.
OpenLDAP logging:
slapd.conf: In /etc/ldap/slapd.conf turn logging on with the line "loglevel 256".
slapd.d: In /etc/ldap/slapd.d/cn=config.ldif please change the attribute "olcLogLevel" to "Stats". Please add a line "olcLogLevel: Stats" if the attribute is missing.
After changing the configuration please restart OpenLDAP. It usually uses /var/log/syslog for log output.