LDAP server receiving huge amount of traffic

We have recently upgraded our LDAP server to AD 2008. When we restarted OpenFire, the LDAP server started receiving a huge amount of queries and continued to receive them for over 12 hours from OpenFire. Eventually, the OpenFire daemon had to be killed as it was impacting other applications.

Anybody have any idea what could be causing this? We are running version 3.6.3 and have a fairly large LDAP directory (>5000 users, ~250 groups).