Well I don't know why comodo isn't getting in there first (it isn't a firewall I have ever used), but it may be a little different to this topic as you are using the earlier version 2.4 without the defence+ module.
It may simply be down to windows booting as there doesn't seem to be any set order in which it loads applications, so avast could be being loaded first.
You could try, uninstall avast, reboot, install, reboot.
It would probably be best to first Download the latest version of avast
http://www.avast.com/eng/download-avast-home.html and save it to your HDD, somewhere you can find it again. Use that when you reinstall.
Then again you could also try using the latest version of the comodo firewall or reinstalling the one you have.
Obviously either of the above options could generate a lot of comodo pop-ups (less if you reinstalled avast) as comodo would have to built its permissions information again.