After many attempts at resolving this problem I came across yet another idea
in the social forums from NYintelligentinvestor, although I have Office 2003
Professional.
See:
http://social.answers.microsoft.com/...5-93a36536d690
Quote
"Okay...I had the same issue with downloading the security updates for
Microsoft 2007. When I tried to install the updates I would receive Error
646. I finally resolved my issue by going to Microsoft's download center and
manually installing myself.
Here are the steps I took...which I believe should work:
1) Go to Microsoft's Download Center:
http://www.microsoft.com/downloads/en/default.aspx
2) Search each update code which starts with the letters "KB" and followed
by a set of numbers (i.e, KB974234)
3) Click the link for the download and then click download and run. I
believe you will have to accept an agreement and then click continue or okay
4) Repeat for all the downloads that you are unable to install
5) Run Microsoft update again and click on check for updates and if the
updates were successfully installed they should no longer appear in the
updates that need to be installed.
...............
"I can't believe all the research and suggestions from techs did not
work.....sometimes your own research is the best! "
End of quote
As (s)he also says - hope it works for you.
Of course it does not answer the question as to why the updates failed in
the first place.
Bill