Some have taken me to task over sharing what I found. My acer did the same and I tracked it down to something plugged into the USB ports. I unplugged all USB devices and the update succeeded as well as the next boot.
I will not enter into any argument here. I will only share my success.
-> If that doesn't work, call Acer and ask for a fix.
In closing there was another failure but it was not a Microsoft or Acer issue. The machine had been damaged (the OS) by trojans. We had to restore the PC then install the updates. Again some take Microsoft to task over this.
My ACER laptop seems to have reached a point where it is working fine yet if I install the latest Windows Vista updates it will fail to boot sucessfully after the reboot. So I have to attempt about 2 or 3 system restores to roll it back to a point where it actually will boot up successfully, however if it takes the updates it happens all over again. Even if I create a manual restore point and accidentally take the updates, if I try to restore to that manual point it still won't work and so I have to keep rolling it back until it eventually works. It's getting very boring now and very very frustrating.
Does anybody have any ideas? Of course I want to take the updates and keep it fresh and up to date but obviously I can't do that at the moment.