Bluetooth blues follow OS X 10.7.4 update

Yesterday Apple released the OS X 10.7.4 update, which addressed a number of problems and security issues in OS X, including the logging of some users' passwords in plain text and the long-standing log-out option for reopening windows always being enabled. Along with this update, however, came a security update to Bluetooth that has caused some people's Bluetooth configurations to not work properly.

The Bluetooth service in OS X 10.7 through 10.7.3 had a bug that meant a local user could potentially hack the Bluetooth daemon process and execute arbitrary code with system privileges, hence Apple's security update. However, a number of Mac users have complained that their Bluetooth setups no longer work after the update. Some are finding their Bluetooth devices don't work and some report problems with Bluetooth audio.

In addition to Bluetooth issues, a few people have had problems with the system no longer showing the closely associated Wi-Fi hardware as being installed.

If you are having trouble with Bluetooth and Wi-Fi connectivity after the OS X 10.7.4 update, there are several things you can try that may get your devices connected again.

1. Disable and re-enable
   While you might first try turning off your Bluetooth devices and turning them back on, often people forget about doing the same with their Macs. Go to the Bluetooth system preferences or to the Bluetooth menu, and choose the option to turn Bluetooth off, and do the same for your Bluetooth devices. Then turn the computer's Bluetooth service on, followed by turning on your Bluetooth devices. Often a simple reset like this is enough to get the devices working again.
2. Restart
   In addition, you can try restarting your system. While you are at it, you might try restarting in safe mode by holding the Shift key down at bootup, and then rebooting again normally. This process will perform some rudimentary cache-cleaning routines and other basic maintenance tasks that are built into the Safe Mode function. In addition to restarting the system, you can try resetting the computer's PRAM and SMC controllers to ensure no odd hardware variables are interfering with the Bluetooth connectivity. Apple has good instructions for how to reset the PRAM and reset the SMC on applicable machines.
3. Unpair your devices
   Quickly toggling the Bluetooth services on and off by disabling Bluetooth or restarting the system will still maintain the existing Bluetooth configurations, so if problems persist, the configuration files may be the root of the issue. You can test this by clearing your Bluetooth devices from your system's configuration and then adding them again.
   
   To do this, go to the Bluetooth system preferences and remove all the Bluetooth devices associated with your system by selecting each one and clicking the minus button. When the devices are removed, click the plus button to add them again, and follow the onscreen instructions to do so.
4. Clear configurations
   Since there could be corruption in areas of the Bluetooth configuration files that are not affected by changing settings in the system preferences, you also can manually remove the configuration files. To clear out these settings, first turn off Bluetooth, and then locate and remove the following files from your system (to access the user library, hold the Option key and click the Go menu in the Finder):
   

   /Macintosh HD/Library/Preferences/com.apple.Bluetooth.plist /username/Library/Preferences/ByHost/com.apple.Bluetooth.UnknownHostID.plist /username/Library/Preferences/com.apple.BluetoothAudio.plist /username/Library/Preferences/com.apple.BluetoothFileExchange.plist

   
   After these files are removed from your system, reboot the computer and then try setting up your Bluetooth devices again.
5. Boot caches and other caches
   While the update to OS X 10.7.4 should have replaced the kernel extensions for Bluetooth and other system features, and then rebuilt the extensions caches and other caches the system uses for quickly booting, this process may not have happened correctly. To address this possibility, you can download and use one of a number of maintenance utilities such as OnyX, MacCleanse, Lion Cache Cleaner, or Yasu, and use them to clear system caches and boot caches. With your utility of choice downloaded, reboot in Safe Mode and then access its options to clear the system caches. You can read more about this in my general maintenance recommendations for OS X.
6. Reapply combo updater or reinstall
   A final step you can try if none of the previous options work is to reapply the OS X 10.7.4 Combo updater, which is available at Apple's Support Web site (it's a 1.4GB download). The updater will contain all of the changed files for OS X since the initial 10.7.0 release, and will replace them with fresh copies. This ensures that none of these files are corrupted and causing problems.
   
   A more in-depth approach to this procedure is to reinstall OS X entirely and then immediately update it to the latest version, which will replace all system files on the computer (while leaving user data and applications intact). To do this, reboot your system to the Recovery HD partition by holding down Command-R at startup. Then choose the option to reinstall OS X and follow the onscreen instructions. After the OS installation is complete, access Software Update and immediately update to the latest version of OS X.

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