< Avast hasn't got an active firewall on > True but other programs can conflict -
With Malwarebytes Anti-Malware, in many early versions you were advised to exclude your choice of Antivirus and Firewall programs, and this did include many free versions also.
For an example, this is shown in Section K of their FAQ
I am not aware of the urls or program settings for Comodo, but it may pay to ask this at the Comodo Forum. - Comodo Firewall, AntiVirus and Defense area.
I have linked the area that relates to Internet Security, but you will need to join the forum to ask a specific question, just like you did here.
Other wise you would follow it from an avast! point of view, as linked by Condobloke -
Thank You -