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.
If this does not help, can you uninstall / boot / install / boot again?
Do you have any other antivirus installed in your computer?
Did you have in the past? Which one?
Do you use a firewall? Which one?
Also, take a look into Administrative Tools > Services
and see how the four avast services are set to start (automatically or manual).
Also, check your system time and date and if your registration is still valid (14 months).