Great news! According to reviews that I have been reading (and my own experience), it appears that OS X Mountain Lion is a pretty stable update with a minimum of major problems, especially for the first release. Still, there are a few bugs that can occasionally cause minor computer problems on your Mac. So it always makes sense to be extra cautious before upgrading to a new version of OS X.
The first thing you should be weary of is to make sure that nothing unusual happens during the install process itself.
Here is one general install tip: After downloading the Install OS X Mountain Lion app from the Mac App Store, you will find it in your Applications folder. Make a copy of the app before proceeding. If you forget this step the app will vanish without a trace after you complete the install (this is a feature that Apple has deliberately enabled, this is not a bug). Ha ha!! Caught you Apple! Don’t worry, you can get Mountain Lion back by re-downloading the app, but keeping a copy saves you time and hassle, in case you ever need to use the Install again.
After you have Mountain Lion installed, and it is up and running, you are not quite home free. Here are some post-installation Mountain Lion problems you may encounter:
Migration Assistant failure
If you try to use the Migration Assistant to migrate to Mountain Lion, you may find that the Assistant app crashes. No need to panic, this is not a huge problem you can still get things working. As Apple explained, all you need to do is uncheck the Back to My Mac item in the iCloud System Preferences on the destination Mac. The Mountain Lion migration should now go through without a hitch. When you are done, you can re-enable the Back to My Mac feature.
According to Apple, “After upgrading to OS X Mountain Lion, your Mac may keep returning to the login window after you have logged in.” If this is a bug that you are experiencing it is clearly an issue you will need to fix ASAP.
The most likely culprit for this OS X problem is an incompatible Login Item. OS X makes an effort to automatically disable incompatible software on startup. However, some apps are still able to sneak in. The solution is to reboot your Mac in Safe Mode (by holding down the Shift key on start up until the gray Apple logo appears). This prevents your Login Items from loading. Now go to System Preferences -> Users & Groups> -> Login Items. Look for any item that “has a non-smoking sign” (a gray circle with a slash) over its icon. This indicates an incompatible item. Delete any such items and restart your Mac normally. Hopefully you will not have any other start up issues after the Login Items fix.
No Wi-Fi after waking from sleep
Numerous users report that, after installing the Mountain Lion upgrade and they wake their Mac laptop or desktop from sleep, the Mac does not automatically re-connect to the local Wi-Fi network. Even worse, the computer will attempt to manually reconnect and may lead to the persistent spinning beachball of death, and making a reconnection is just about impossible.
One solution that has worked for some users is to:
- Go to Network System Preferences and click the Advanced button
- Delete all the known networks under the Wi-Fi tab
- Return to the main Network display and delete Wi-Fi from the Services list
- Now add a new Wi-Fi service (by clicking the + icon at the bottom of the list section)
Unfortunately, this is not a sure-fire fix for all users. Many Apple users with this symptom continue to struggle to find a resolution. A few people have suggested that an incompatible third-party software is the root cause for this OS X problem. Another solution is a few Mac users have found that turning off Bluetooth eliminates this symptom.
Bluetooth-related kernel panic after waking from sleep
Another bug you may experience is if you turn off all your Bluetooth-connected devices while your Mac is asleep, a kernel panic may occur when you wake up the Mac. If you have gone further and disabled “Allow Bluetooth devices to wake this computer,” located in the Advanced section of Bluetooth System Preferences, a kernel panic may occur even if you leave the Bluetooth devices on. Industry experts believe that the cause is a bug that Apple will likely fix in 10.8.1. Leaving the ’Allow Bluetooth devices to wake this computer’ preference enabled can lower chances of a kernel panic when waking from sleep.
Mail replies from wrong address
Apple Support Communities report that the new version of Mail in Mountain Lion has trouble assigning the correct address for email replies. If you have more than one email account, when you reply to an email, Mail should use the account that received the message as your “from” address. This should override any selection you have made for a default address to use with new messages. Unfortunately this does not always happen in Mountain Lion.
The problem is that Mail may now use your default address for replies, and ignores that the received message comes from a different account. Postings in the Apple community forum thread offer some potential workarounds, but so far there are no outright fixes. Also it is possible that you may not see this symptom at all.
Safari 6’s Top Sites Updates are gone?
Mountain Lion OS X includes Safari 6 (you can also download the updated browser to run in Lion). According to more than a dozen posts on an Apple Support Communities thread, there is a minor glitch with the apps’ Top Sites feature. The white star that should appear in the corner of a listed page, when the page gets updated, no longer shows up. There is no known fix as of yet. This is another bug that Apple will need to address. [Update: Reader comments in Apple’s Support Communities indicate that the symptom is a byproduct of Apple removing the RSS support from Safari 6. In other words, it is not a bug; it is a feature.]
I will follow up with any fixes to any of these issues as they come out.