1 don't disable your router firewall. Comodo might be good but it doesn't replace it.
2 I never had issues between CIS and Avast, i.e. nothing was blocked, but according to another thread, it seems that yes in some cases, although I wonder how...anyway, delete all CIS rules related to Avast (in both Def+ and the firewall) and reboot. Depending on your mode you'll be prompted to recreate these rules or this will be done automatically. Best thing is to put both the firewall and def+ in "training mode" before rebooting, wait until all avast processes have run (do a manual update), and then turn def+ and the firewall back to your preferred modes. You should be able to update then. Again, I've never experienced this problem, CIS always created immediately appropriate rules for Avast on my system. So if it's not that on your system, I have no idea. More and more people are currently complaining about updating issues and avast services problems too. I had one update issue earlier today but it was solved after a reboot.