Networking :: Openldap Upgrade From 2.3.32 To 2.4.23 - Error 'no Structural Object Class Provided'

Currently I have a single openldap server version 2.3.32 preforming authentication on our databases as well as e-mail and other assorted programs. When we get a high volume of users, sometimes the users can not be authenticated for new e-mail sessions and what not. We have traced it back to being that our current single ldap server can not authenticate them all in a timely manner. We decided that we would put up a new ldap server and replicate the changes to it, then upgrade the older server version and replicate back to it so that both would have a current up to date copy of our configuration, and we would do a master/slave type setup.

Trying to replicate between the old server and the new server is not currently working. Here is the issue: when we try to import the schema's from the older server we get this error: slapadd: dn="cn=Domain Users,ou=Groups,dc=mydomain,dc=com" (line=247): (65) no structural object class provided I can not seem to find any information on google that shows this exact error? if this isn't detailed enough let me know what else I should post.