XML Core Services 6.0 Service Pack 2 (KB954459) doesn't hold

I have an Automatic Updates message on my systray. It tells me to install this update immediately. Everytime I install it, within seconds the update icon reappears and tells me to install the same update. I looked in the update history section and it shows I’ve installed it 8 times (as many times as I have attempted).

Security Update for Microsoft XML Core Services 6.0 Service Pack 2 (KB954459)

I’ve scanned with I’ve used CCleaner, MBAM and SAS and it reports no issues.

No problems were found although ctrl+alt+del or calling the taskmanager using right-click on the task bar cause avast to report wuauclt.exe is infected with win32: Spyware-gen [Trj], and deletes the file.

If I ctrl+alt+del before I replace the wuauclt.exe file with a clean copy, the computer creates an infected wuauclt.exe file on its own and infects msconfig.exe file. I can’t delete the wuauclt file but I can rename and delete it using file assassin. Then I have to go into HJT and delete a wuauclt.exe entry and turn off a startup call to wuauclt.exe.

I just tried to run HJT and save a logfile and it triggered the same avast infection message (although I was able to run it and posted results yesterday). Also when I try to simply open Notepad via the start menu or double-click a file with a TXT or LOG ext, it triggers the avast infection detection and deletion process. If I double-click notepad.exe (in the Windows dir) it open fine.