Please, avoid CAPS... forum policy, you're not screaming...
Did you uninstall AVG before trying to use avast?
Which is your firewall?
avast does not change or mess any favorite sites list and does not block the access to them, unless they're infected.
To uninstall avast:
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.