We will need more information to be able to help you:
- Which OS are you using? Is it up to date?
- What avast! version number?
- Do you use a firewall? Which one?
- Do you have any other antivirus installed in your system? Did you have in the past?
- Any other security programs that could interfere?
I suggest an installation from the scratch:
1. Uninstall avast from Control Panel first.
2. Boot.
3. Download the latest version of
Avast Uninstall and use it for complete uninstallation.
4. Boot.
5. Install again the latest
avast! version.
6. Boot.
7. Check and post the results.