1. Is your system time and date correct?
2. Is your avast well installed and updated?
3. Can you try to repair your installation? Go to Control Panel > Add/Remove programs > avast! antivirus > Remove. Then choose Repair function in the popup window (Repair). You must be connected to the internet while repairing.
4. Do you use any other antivirus in your computer?
5. If this does not help, can you uninstall / boot / install / boot again?
6. If nothing helps the problem is that sometimes, Windows Security Center stop recognizing your antivirus or firewall... The fix could be fairly easy for the most part.
1. Go to control panel and open Administrative tools.
2. Click on services.
3. Go down to Windows Management Instrumentation.
4. Stop this service. Stop Security Center service too.
Let them to Automatically start.
5. Exit out of this area to your desktop.
6. Right click Start and choose Explore.
7. Go to c:\windows\system32\wbem\repository.
Delete this subdirectory
ONLY. Let the others there.
Sometimes, only using
Unlocker,
MoveOnBoot or
Delete FXP you can delete these files.
8. Exit back to your desktop and reboot your computer (maybe you need to boot twice).
This will rebuild the deleted folder and the database. Once restarted, Windows Security Center should show the correct info and antivirus and firewall should now be recognized