@ propheticus,
Not clear if you disabled the Windows Firewall first before install of the 2014 AIS version. I've also noted that the aswNdis, aswNdis2, and aswNdisFlt (XP/Win 7 drivers) sometimes remained after using aswclear.exe and needed to be removed manually. To do that, open Device Manager and click View>Show hidden devices. Then click Network Adapters. When done, change back to 'View>Devices by type' if that's how you've set it up.
If these drivers are still present even after uninstalling AIS 2014 or 2015, then they may interfere with proper operation of avast firewall, if you choose to try again. At least worth a check.
Also ensure Windows Firewall is not running on install of AIS. avast firewall and windows firewall are meant to run together, but experience has shown that this does not work on all machines.