Like you i had the same issue,but i had three entries of Firewall NDIS Filter Miniport with yellow symbols.So i did a clean install
then after Avast was uninstalled i went to device manager and uninstalled the three Firewall NDIS Filter Miniport with yellow symbols,
then reinstalled Avast IS,and rebooted.
Then when i go back to check device manager the three Avast Firewall NDIS Filter Miniport have disappeared.
Is this normal?I thought they would have reappeared without the yellow exclamation symbols.