Just a couple of comments. After repair, or after installation anew, you should reboot IMMEDIATELY before testing anything else, including configurations, scanning or updates.

ONLY if the clean re-installation doesn’t solve the problem (which, if performed correctly, it should), you could use the web contact form:
http://www.avast.com/contact-form.php?loadStyles.

May I ask, before Avast, which security tools were you using?

A partial list of specific removal utilities for many security tools is located at http://thewebatom.net/uninstallers/security-software/, so cleaning up remnants of previous security tools may solve conflicts too.