I use AWC with avast and no problems...
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.
I suggest an installation from the scratch:
1. Uninstall avast from Control Panel first.
2. Boot.
3. Use
Avast Uninstall for complete uninstallation.
4. Boot.
5. Install again the last version.
6. Boot.
7. Check and post the results.