This problem with the Windows Security Center - WSC and later Windows Action Center - WAC (failing to recognise AV installations) has been going on for many, many years in XP, Vista, Win7 and now Win8 and has been answered many times.
So to have to continually come back to say the same thing (as has been said here) is somewhat over the top.
The solution has also been mentioned at length in many topics, by disabling avast and enable it again, seems to jump start the WAC. Right click the avast tray icon, avast! Shield Control - Disable for 10 minutes - don't wait 10 minutes a few seconds should be enough and then enable them again.