I also started seeing the Win7-64 Action Center message on my system about 3 or 4 days ago also (Windows did not find anti-virus software on this computer). Maybe the latest program updates broke something, dunno. I will add that about 10 days ago I noticed that Avast was disabled and not running. I tried re-enabling it but kept getting an error message. I then un-installed Avast Free and re-installed it. Ran a complete system scan and no threats found. Now after a few updates Win7 Action Center thinks Avast does not exist but it seems to be running just fine. Complete system scans still show no threats.

Maybe I should try that special un-install utility and then re-install Avast Free. I don’t like the alternative idea of turning off the Windows Management items because of a conflict between Avast and Win7-64, if there is one.