Mysterious NT Licensing Issue

Every time I delete users in the User Manager for Domains and try to remove old licenses and wait a few days, the deleted licenses reappear. When I view the License Manager lists I see users that don’t exist anymore. I purge them and all is fine until I reboot the server; then the deleted user licenses show up again after a week or so. Is there a registry hack or fix that will remedy this issue?

Thanks in advance,
Damian