iMacは正常にシャットダウンせず、永久にロードループのままです。

iMacを終了しようとするたびに、ロードループに永遠に閉じ込められます。電源を切る唯一の方法は、電源ボタンを長押しすることです。システムログ（下）を確認しましたが、シャットダウンが永久に繰り返される原因が見つかりませんでした。どんなアイデアがありますか？

Sep 18 06:47:50 Tardis.local GoogleSoftwareUpdateDaemon[3270]: -[KSUpdateCheckAction(PrivateMethods) finishAction] KSUpdateCheckAction found updates: {( )}
Sep 18 06:47:50 Tardis.local GoogleSoftwareUpdateDaemon[3270]: -[KSPrefetchAction performAction] KSPrefetchAction no updates to prefetch.
Sep 18 06:47:50 Tardis.local GoogleSoftwareUpdateDaemon[3270]: -[KSMultiUpdateAction performAction] KSSilentUpdateAction had no updates to apply.
Sep 18 06:47:50 Tardis.local GoogleSoftwareUpdateDaemon[3270]: -[KSMultiUpdateAction performAction] KSPromptAction had no updates to apply.
Sep 18 06:47:50 Tardis.local GoogleSoftwareUpdateDaemon[3270]: -[KSUpdateEngine(PrivateMethods) updateFinish] KSUpdateEngine update processing complete.
Sep 18 06:47:53 Tardis.local com.apple.usbmuxd[1629]: _SendDetachNotification (thread 0x7fff744ab180): sending detach for device d0:23:db:1b:9a:fa@fe80::d223:dbff:fe1b:9afa._apple-mobdev._tcp.local.: _BrowseReplyReceivedCallback got bonjour removal.
Sep 18 06:48:03 Tardis.local com.apple.SecurityServer[20]: Succeeded authorizing right 'system.volume.removable.unmount' by client '/System/Library/CoreServices/Finder.app' [3219] for authorization created by '/System/Library/CoreServices/Finder.app' [3219] (100013,0)
Sep 18 06:48:03 Tardis.local com.apple.SecurityServer[20]: Succeeded authorizing right 'system.volume.removable.unmount' by client '/usr/sbin/diskarbitrationd' [56] for authorization created by '/System/Library/CoreServices/Finder.app' [3219] (100002,0)
Sep 18 06:48:05 Tardis.local webfilterproxyd[3277]: whitelistVerdict: (null) | kitty has no web restrictions | http://init.ess.apple.com/WebObjects/VCInit.woa/wa/getBag?ix=1
Sep 18 06:48:05 Tardis kernel[0]: Sandbox: sandboxd(3279) deny mach-lookup com.apple.coresymbolicationd
Sep 18 06:48:05 Tardis.local webfilterproxyd[3277]: whitelistVerdict: (null) | kitty has no web restrictions | https://tools.google.com
Sep 18 06:48:05 Tardis.local sandboxd[3279] ([3277]): webfilterproxyd(3277) deny job-creation
Sep 18 06:48:07 Tardis.local GoogleSoftwareUpdateDaemon[3270]: -[KeystoneDaemon logServiceState] GoogleSoftwareUpdate daemon (1.1.0.3659) vending:
        com.google.Keystone.Daemon.UpdateEngine: 1 connection(s)
        com.google.Keystone.Daemon.Administration: 0 connection(s)
Sep 18 06:48:09 Tardis.local com.apple.SecurityServer[20]: Succeeded authorizing right 'system.volume.removable.unmount' by client '/System/Library/CoreServices/Finder.app' [3219] for authorization created by '/System/Library/CoreServices/Finder.app' [3219] (100013,0)
Sep 18 06:48:09 Tardis.local com.apple.SecurityServer[20]: Succeeded authorizing right 'system.volume.removable.unmount' by client '/usr/sbin/diskarbitrationd' [56] for authorization created by '/System/Library/CoreServices/Finder.app' [3219] (100002,0)
Sep 18 06:48:15 Tardis.local GoogleSoftwareUpdateDaemon[3270]: -[KeystoneDaemon main] GoogleSoftwareUpdateDaemon inactive, shutdown.
Sep 18 06:48:19 Tardis com.apple.launchd.peruser.502[277] (com.apple.PackageKit.InstallStatus): Throttling respawn: Will start in 9 seconds
Sep 18 06:48:19 Tardis.local WindowServer[106]: CGXGetConnectionProperty: Invalid connection 85271
Sep 18 06:48:19 --- last message repeated 4 times ---
Sep 18 06:48:19 Tardis.local WindowServer[106]: dict count after removing entry for window 0x56c is 0
Sep 18 06:48:19 Tardis com.apple.launchd.peruser.502[277] (com.apple.unmountassistant.useragent[3300]): Exited: Killed: 9
Sep 18 06:48:19 Tardis.local coreservicesd[68]: SendFlattenedData, got error #268435459 (ipc/send) invalid destination port from ::mach_msg(), sending notification kLSNotifyApplicationDeath to notificationID=1538
Sep 18 06:48:19 Tardis com.apple.launchd.peruser.502[277] ([0x0-0x35f35f].com.apple.iTunesHelper[3263]): Exited with code: 1
Sep 18 06:48:19 Tardis.local coreservicesd[68]: SendFlattenedData, got error #268435460 (ipc/send) timed out from ::mach_msg(), sending notification kLSNotifyApplicationDeath to notificationID=1589
Sep 18 06:48:19 Tardis com.apple.launchd.peruser.502[277] (com.apple.mdworker.bundles[3289]): Exited: Killed: 9
Sep 18 06:48:19 Tardis.local WindowServer[106]: CGXGetConnectionProperty: Invalid connection 85271
Sep 18 06:48:20 --- last message repeated 4 times ---
Sep 18 06:48:20 Tardis.local loginwindow[3076]: DEAD_PROCESS: 3076 console
Sep 18 06:48:20 Tardis.local coreservicesd[68]: SendFlattenedData, got error #268435460 (ipc/send) timed out from ::mach_msg(), sending notification kLSNotifyApplicationReady to notificationID=1532
Sep 18 06:48:20 Tardis.local airportd[3194]: _doAutoJoin: Already associated to “Type 40 Tardis”. Bailing on auto-join.
Sep 18 06:48:20 Tardis.local WindowServer[106]: CGXGetConnectionProperty: Invalid connection 85271
Sep 18 06:48:20 --- last message repeated 9 times ---
Sep 18 06:48:20 Tardis.local shutdown[3308]: halt by kitty: 
Sep 18 06:48:20 Tardis.local shutdown[3308]: SHUTDOWN_TIME: 1347976100 852452