I seem to have solved my issue concerning updates to .NET Framework.
I'm sorry but I cannot inform whether had anything to do with 'Attacks on the Windows Help and Support Center Vulnerability (CVE-2010-1885)', despite my suspicion that something had gone amiss in Microsoft Update routine. Ultimately, I reinstall / upgrade Windows Installer using the following link -
http://www.microsoft.com/downloads/details.aspx?familyid=5A58B56F-60B6-4412-95B9-54D056D6F9F4&displaylang=enThen I installed the remaining .NET downloads. The install process seemed labored but did complete with KB974417 being the final install. I was informed by Microsoft Update that I had hidden this install for the time being, something which I cannot recall doing, or in fact do not know how to do. (but in the heat of a moment I may have been presented with an option and followed the recommendation).
Now for Trojan:Win32/Orsam!rts -
figuring I had an MS issue and so could be solved by MS itself, I downloaded and ran Microsoft Security Essentials, which generated the orsam detection when I chose to run the Internet Explorer browser at one stage. As far as I can tell - but almost certainly - the orsam detection was a False Positive generated by having both MSE and avast!antivirus running as resident on the same system.