A while ago we reported on an issue where MacBook users were experiencing an intermittent 30-second freeze on their systems (, ). For many people it was usually accompanied by a small clicking sound, indicating a problem with the hard drive. Apple addressed this issue by releasing a hard drive firmware update, but it appears similar problems are persisting.
In a lengthy Apple Discussion thread, users are still complaining of random freezing in their MacBooks. Unfortunately there does not seem to be much of a unifying theme to the freezes. Previously, the problem would happen for a 30-second interval and then unfreeze; however, currently some systems are not unfreezing, and others are showing more erratic pauses.
There are more than likely multiple reasons for the various symptoms being described, which can stem from software setup issues to firmware incompatibilities, so to troubleshoot the issues, try the following suggestions:
Boot into Safe Mode
Doing this will prevent any third-party extensions or applications (i.e., hardware or network monitoring utilities) from launching at bootup, which may be contributing to the problem, especially if they're not fully compatible with the most recent OS update.
Troubleshoot applications and user settings
Along with Safe Mode (especially if Safe Mode shows promising results), you can test your software setup by quitting or removing various applications you have installed. A number of people have had issues with various programs, including those that synchronize with network resources (i.e., Mail managing a corrupt RSS feed, or the third-party TextExpander tool having problems with MobileMe).
Application-specific problems may be from problems with your user account, so try creating a new one, logging in with it, and testing the various programs you use. If the problem continues then your account's settings are not to blame, and it's likely a reinstallation of the application will help. Specific applications to look for include those that run in the menu bar (called "Menu Extras") and system or application add-ons such as Internet plug-ins, audio-units, and system "haxies".
Run a SMART checker
Apple's Disk Utility will check the SMART status of internal drives (seen at the bottom of the window with the drive device selected); however, I recommend you use another utility as well. The SMART measurements that each utility reads can vary, so using another one may help. Ones that can at regularly or continuously check the SMART stats such as SMARTReporter or SMART Utility may be particularly beneficial for monitoring changes when the hangs occur.
Run general maintenance
Clearing system caches and running maintenance scripts may help these situations, so try using a cleaning application such as OnyX, Yasu, Cocktail, or [Snow] Leopard Cache Cleaner (among others) to run these routines. Additionally, you may consider reapplying the latest "Combo" updater for your OS version, which can be searched for and downloaded from Apple's support site. Run these maintenance routines and the combo installer after booting into Safe Mode to ensure minimal interference when they are running.
Downgrade or reinstall
Some people have had success either by downgrading to a previous version of OS X, or by reinstalling the system altogether. First make sure you have a full backup of your system (cloning, or with Time Machine), and then boot off the installation DVD. Try a standard installation to perform a default "Archive and Install", and if that does not work, first run Disk Utility to fully partition and reformat the hard drive before running the installer. Then use Migration Assistant to restore your files and settings from the backup. With a fresh copy of OS X installed, run the latest "Combo" system updater for the desired version of OS X.
If these do not help either fix or indicate the root of the problem, you can further test your hardware setup in the following ways:
Remove all peripheral devices
Either conflicts between devices, or the inability to power all devices connected to your system may be a reason for pauses and slow-downs. To troubleshoot, just disconnect them all (printers and USB hubs included) and reboot your system. If this shows improvement, try reconnecting them one at a time to test each, and then try alternate ways of connecting them to your system (use as little daisy-chaining as possible).
Boot off an external drive
If you have an external hard drive handy, try installing your OS to it and booting off of it. It would be preferable to use a system cloning utility such as Carbon Copy Cloner or SuperDuper and do a block-level clone since this will preserve your current OS installation and software setup as much as possible. Boot to the drive (hold the "Option" key at startup to get to the boot menu) and see if that shows similar pausing behaviors. When doing this, use Disk Utility to fully unmount the internal drive so the system does not interact with it. If the pauses do not persist, then your internal drive may be faulty, or there may be incompatibilities between it and the system's firmware.
Change the internal drive
Pending the results of testing your drive by booting off an external one, you may have to replace your internal drive. While Apple updated the hard drive firmware for the initial freezing problem with MacBook computers, there is no telling whether Apple will do this again. Your best bet in the event of a hardware malfunction or incompatibility would probably be to make a clone of your drive (make two for extra precaution) and then replace the drive and clone your data back.