Office SP1 Update Failing on Vista

When Windows Update tries to install Office SP1 Update on my Vista system I
get a message which says ... "Windows has encountered a critical problem and
will restart automatically in one minute. Please save your work now." There
is no other failure indication.

After the auto reboot the power off button shows the indicator that changes
will be applied during power off - and if I go through another reboot cycle
this clears - but windows update still says I need to install the Office SP1
Update.

The install log shows Install failed with error 80070643 - but I notice that
this is not from the latest install attempt since I have tried several times
but there is only one entry in the log and that is from from 8 hours ago.


Additional information ...

I got the first of these "Windows has encountered a critical problem and
will restart automatically in one minute. Please save your work now."
messages when I was trying to install Acronis True Image 11. It told me that
there was an install of office update that was pending. So after the
TrueImage install failure I used system restore to go back to a restore point
prior to doing anything with Acronis and then tried to do a complete windows
update to make sure nothing was pending before I tried again.

Obviously I have no idea which of the following is true
1. There is no connection between the failures.
2. The failed Office Update caused the Acronis Install to fail
3. The failed Acronis install corrupted something.
4. Some combination of 2 or 3.

I'd appreciate some guidance on how to clean everything up and start again.

Thanks in advance.


--
Paul G