Just been having fun with uninstalling and hiding a problematic Office 2010 update.
I found I could not open MS Update Website whilst Avast shields were active. See attached. Seems to be reporting a Certificate issue.
I had no problem using MS Update website once avast shields were turned off (temporarily). I was then able to do the job I wanted to do there, i.e. hiding the offending update from being offered again in future.
Some good news to share.
After some searching I think I have found a solution, unrelated to Avast.
This involved fixing microsoft update, by running MicrosoftFixit50202.msi tool on the affected XP machine.
I can now access update.microsoft.com on that machine without Avast returning a Revoked Certificate error and blocking access to the website.
NB: That tool is no longer available or supported by Microsoft, but I had a copy of it in archive.