Uninstall the other AV that has a firewall. Use CCleaner to clean-up any leftovers. The other AV may still be causing conflicts even with it turned off.

For a free firewall that works well with avast try;
http://www.filehippo.com/download_outpost_firewall/
http://www.softpedia.com/get/Security/Firewall/Online-Armor-Free.shtml
http://www.softpedia.com/get/Security/Firewall/Privatefirewall.shtml :slight_smile:

If you are a novice I recommend using Private Firewall. Be sure to make the proper exclusions.