HT201262 No start up after software update?

Question

I have been unable to restart me computer after a software update (White screen/apple logo/spinning wheel continuously). I have tried to start up in safe mode (holding down shift key) but it hasn't worked. Any ideas?
Thanks

Answer 1

General advice on updating:
It is worth noting that it is an extreme rarity for updates to cause upsets to your system, as they have all been extensively beta-tested, but they may well reveal pre-existing ones, particularly those of which you may have been unaware. If you are actually aware of any glitches, make sure they are fixed before proceeding further.
So before you do anything else:
If you can, make a full backup first to an external hard disk. Ideally you should always have a bootable clone of your system that enables you to revert to the previous pre-update state.
Turn off sleep mode for both screen and hard disk.
Disconnect all peripherals except your keyboard and mouse.
1. Repair Permissions (in Disk Utility)
2. Verify the state of your hard disk using Disk Utility. If any faults are reported, restart from your install disk (holding down the C key), go to Disk Utility, and repair your startup disk. Restart again to get back to your startup disk.
At least you can now be reasonably certain that your system does not contain any obvious faults that might cause an update/upgrade to fail.
3. Download the correct version of the COMBO update from the Apple download site. If your car runs on gasoline you would not want to fill the tank with diesel, so don’t try to install the PPC updater on an Intel Mac!
The 10.4.11 Combo Updater for PPC Macs is here:  http://support.apple.com/kb/DL170
And for Intel Macs here:  http://support.apple.com/kb/DL172
If you prefer to download updates via Software Update in the Apple menu (which would ensure that the correct version for your Mac was being downloaded), it is not recommended to allow SU to install major (or even minor) updates automatically. Set Software Update to just download the updater without immediately installing it. There is always the possibility that the combined download and install (which can be a lengthy process) might be interrupted by a power outage or your cat walking across the keyboard, and an interrupted install will almost certainly cause havoc. Once it is downloaded, you can install at a time that suits you. You should make a backup copy of the updater on a CD in case you ever need a reinstall.
Full details about the 10.4.11 update here:  http://support.apple.com/kb/TA24901?viewlocale=en_US
More information on using Software Updater here:
http://support.apple.com/kb/TA24901?viewlocale=en_US
Using the Combo updater ensures that all system files changed since the original 10.4.0 are included, and any that may have been missed out or subsequently damaged will be repaired. The Delta updater, although a temptingly smaller download, only takes you from the previous version to the new one, i.e. for example from 10.4.10 to 10.4.11. Software Update will generally download the Delta updater only. The preferable Combo updater needs to be downloaded from Apple's download site.
Now proceed as follows:
4. Close all applications and turn off energy saving and screensaver.
5. Unplug all peripherals except your keyboard and mouse.
6. Install the update/upgrade. Do not under any circumstances interrupt this procedure. Do not do anything else on your computer while it is installing. Be patient.
7. When it ask for a restart to complete the installation, click restart. This can take longer than normal, there are probably thousands of files to overwrite and place in the correct location. Do nothing while this is going on.
8. Once your Mac is awake, repair permissions again, and you should be good to go!
If your Mac seems slightly sluggish or ‘different’, perform a second restart. It can’t hurt and is sometimes efficacious!
9. Open a few of your most used applications and check that all is OK. In this connection please remember that not all manufacturers of third party applications and plug-ins, add-ons, haxies etc, will have had time to do any necessary rewrites to their software to make them compliant with the latest version of your operating system. Give them a weeks or two while you regularly check their websites for updates. This applies particularly to plug-ins for Safari 3.
N.B. Do not attempt to install two different updates at the same time as each may have different routines and requirements. Follow the above recommendations for each update in turn.
Lastly, Apple's own article on the subject of Software Update may also be useful reading:
http://docs.info.apple.com/article.html?artnum=106695
[b]If you are updating Safari (or just have):[/b]
Input Managers from third parties can do as much harm as good. They use a security loophole to reach right into your applications' code and change that code as the application starts up.  If you have installed an OS update and Safari is crashing, the very [i]first[/i] thing to do is clear out your InputManagers folders (both in your own Library and in the top-level /Library), log out and log back in, and try again.
So, disable all third party add-ons before updating Safari, as they may not have been updated yet for the new version. Add them back one by one. If something goes awry, remove it again and check on the software manufacturer's website for news of an update to match your version of Safari. Remember: Tiger up to 10.4.10 used Safari 2.0.4 or, if you downloaded it, Safari 3.0.3 beta. Safari 10.4.11 used Safari 3.0.4 which was [i]not[/i] a beta. If Safari 3.1.2 on 10.4.11 is not the fastest browser you have ever used, then something is wrong!
Moreover, trying to revert to Safari 3.0.4 (or worse still, version 2) when running 10.4.11 or 10.5 can have repercussions, as Safari 3.1.1 uses a completely different webkit on which other applications like iChat, Mail and Dashboard Widgets etc also rely, and may entail you having to reinstall an earlier operating system.
[b][i]Most errors reported here after an update are due to an unrepaired or undetected inherent fault in the system, and/or a third party ad-on.[/b][/i] Two such add-on that have been frequently mentioned here for causing such problems are Piclens and Pithhelmet. If you have them, trash them.
Additional tips on software installation here:
http://docs.info.apple.com/article.html?artnum=106692
To reiterate, Input Managers reach right into an application and alter its code. This puts the behavior of the affected application outside the control and responsibility of its developers: a recipe for  problems. That's not to say that issues absolutely will ensue as a result of Input Managers, but you, as a user, must decide. If the functionality of a specific Input Manager or set thereof is really important to you, you may well choose to assume the associated risk.
Again, the advice is to remove all Input Managers from the following directories:
/Library/InputManagers
~/Library/InputManagers
especially prior to system updates (they can always be added back one-by-one later).