Updates not installing on Mac OS X

Problem

This applies to Mac OS X 10.4-10.7

You are trying to install updates on your Mac and the system does not progress through the update.
This can lead to the user switching off the computer prematurely and possibly corrupting the updates cache that can also lead to machine  not booting correctly.

Solution

1. Switch the machine on into Single User mode.  Hold the Apple (command key) and S key (together when switching on the computer)  This will present a Black screen with white writing (Let go off the keys when you see this screen).
2. Firstly you will need to mount the drive by using the following command:
   mount -uw /
3. To remove the updates cache, type the following:
4. rm -rf /Library/Updates/*
   This will remove the updates cache from the system.
5. Then type the following:
   reboot
   The machine should now update correctly.