Reason is that I can no longer get Microsoft updates to run so I wrote to Microsoft and they have come back with several suggestions. The one I'm into now tells me to first shut down my antivirus temporarly.
I would consider that Microsoft Bull.
I've never come across any program that actually requires turning off avast!.
avast! is always running and there aren't any problems receiving auto updates from MS.
It was that way while I had XP, Vista and now Windows 7.