"Unable to rename user" errors when attempting to login with a LDAP user

2013-10-11 22:19:58,407 ERROR [http-8443-6] [[Standalone].[localhost].[/c530].[action]] log Servlet.service() for servlet action threw exception
java.lang.IllegalStateException: Unable to rename user Horatio Nelson to horatio nelson
	at com.atlassian.crowd.directory.AbstractInternalDirectory.forceRenameUser(AbstractInternalDirectory.java:611)
	at com.atlassian.crowd.directory.DelegatedAuthenticationDirectory.authenticateAndUpdateOrCreate(DelegatedAuthenticationDirectory.java:218)
	at com.atlassian.crowd.directory.DelegatedAuthenticationDirectory.authenticate(DelegatedAuthenticationDirectory.java:175)

private User authenticateAndUpdateOrCreate(String name, PasswordCredential credential)
            throws InactiveAccountException, ExpiredCredentialException, OperationFailedException, InvalidAuthenticationException, UserNotFoundException
    {
        // authenticate the user against LDAP
        User ldapUser = ldapDirectory.authenticate(name, credential);
        // Try to find the corresponding local user
        User internalUser = findLocalUserByExternalId(ldapUser.getExternalId());
        if (internalUser != null)
        {
            if (!internalUser.getName().equals(name))
            {
                // We want to rename the existing user
                if (isUserUpdateOnAuthEnabled())
                {
                    // push any existing user out of our way and rename
                    try
                    {
                        internalUser = internalDirectory.forceRenameUser(internalUser, name);
                    }
                    catch (UserNotFoundException e)
                    {
                        // Pretty unlucky
                        throw new ConcurrentModificationException("Unable to rename '" + internalUser.getName() + "' to new name '" + name + "' during login.");
                    }
                }

if (!internalUser.getName().equals(name))