You have two solutions for now; until the CPF team resolve the problem.
1-Open the AVG control center, and click in email scanner. Go to general settings and click the box ignore faulty condition of the compenent. Restart the computer and try the thunderbird.
Or
2-with the windows firewall on, click in comodo “allow all” and start the thunderbird after reading all your emails, come back to CPF and change the security settings again