Update userName from LDAP failed

2013-09-02 10:46:23,853 QuartzScheduler_Worker-0 ERROR ServiceRunner     [atlassian.crowd.directory.DbCachingDirectoryPoller] Error occurred while refreshing the cache for directory [ 3 ].
com.atlassian.crowd.exception.OperationFailedException: Unable to rename user 'ut1gbh' to 'UT1GBH', please perform full synchronization.
        at com.atlassian.crowd.directory.DbCachingRemoteChangeOperations.updateUsers(DbCachingRemoteChangeOperations.java:232)
        at com.atlassian.crowd.directory.DirectoryCacheImplUsingChangeOperations.addOrUpdateCachedUsers(DirectoryCacheImplUsingChangeOperations.java:59)
        at com.atlassian.crowd.directory.ldap.cache.UsnChangedCacheRefresher.synchroniseUserChanges(UsnChangedCacheRefresher.java:220)
        at com.atlassian.crowd.directory.ldap.cache.UsnChangedCacheRefresher.synchroniseChanges(UsnChangedCacheRefresher.java:81)
        at com.atlassian.crowd.directory.DbCachingRemoteDirectory.synchroniseCache(DbCachingRemoteDirectory.java:667)
        at com.atlassian.crowd.manager.directory.DirectorySynchroniserImpl.synchronise(DirectorySynchroniserImpl.java:75)
        at com.atlassian.crowd.directory.DbCachingDirectoryPoller.pollChanges(DbCachingDirectoryPoller.java:50)
        at com.atlassian.crowd.manager.directory.monitor.poller.DirectoryPollerJob.execute(DirectoryPollerJob.java:34)
        at org.quartz.core.JobRunShell.run(JobRunShell.java:195)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:520)
Caused by: com.atlassian.crowd.exception.UserAlreadyExistsException: User already exists in directory [3] with name [UT1GBH]
        at com.atlassian.crowd.directory.AbstractInternalDirectory.renameUser(AbstractInternalDirectory.java:559)
        at com.atlassian.crowd.directory.DbCachingRemoteChangeOperations.updateUsers(DbCachingRemoteChangeOperations.java:226)
        ... 9 more

if (!remoteUser.getName().equals(internalUser.getName()))
                {
                    logger.warn("remote username [ {} ] casing differs from local username [ {} ]. User details will be kept updated, but the username cannot be updated", remoteUser.getName(), internalUser.getName());
                }
                if (hasChanged(remoteUser, internalUser))
                {
                    final UserTemplate userToUpdate = makeUserTemplate(remoteUser);
                    // Ensure that the username will not be updated
                    userToUpdate.setName(internalUser.getName());
                    // Ignore active flag value from remote directory and manage it locally if the remote directory does not support active flag.
                    if (!remoteDirectory.supportsInactiveAccounts())
                        userToUpdate.setActive(internalUser.isActive());
                    usersToUpdate.add(userToUpdate);
                }
                else
                {
                    logger.trace("user [ {} ] unmodified, skipping", remoteUser.getName());
                }

final User currentUser = internalDirectory.findUserByExternalId(externalId);
								try
								{
									if (!StringUtils.equals(currentUser.getName(), user.getName()))
									{
										internalDirectory.renameUser(currentUser.getName(), user.getName());
									}
								}
								catch (UserAlreadyExistsException e)
								{
									// Make sure that one bogus user coming over the wire doesn't hose the entire sync.
									throw new OperationFailedException("Unable to rename user '" + currentUser.getName() + "' to '" + user.getName() + "', please perform full synchronization.", e);