If you rename a User account and only the case changes, the account change will not be replicated. Since the User account is not case sensitive, the Netlogon Service will not ask the SAM on the BDC to change the account. To workaround this feature:
1. Rename the account (JOHNDOE) to JSIacct.
2. Synchronize the BDCs with the PDC.
3. Rename JSIacct to JohnDoe.
4. Synchronize the domain.